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JOURNAL ABSTRACTS

Longitudinal changes in anterior chamber depth and axial length in Asian subjects after trabeculectomy surgery.

Husain R1, Li W, Gazzard G, Foster PJ, Chew PT, Oen FT, Phillips R, Khaw PT, Seah SK, Aung T.

Abstract
BACKGROUND/AIMS:
To investigate longitudinal changes in anterior chamber depth (ACD) and axial length (AXL) over 5 years after trabeculectomy surgery in Asian patients with primary glaucoma, and to identify factors associated with these changes.

METHODS:
In this prospective cohort study, phakic subjects with primary glaucoma who underwent trabeculectomy had ACD and AXL measured over 5 years. The effect of intraocular pressure (IOP) on ACD and AXL was determined. Subjects were divided into two groups (high or low fluctuation of ACD/AXL) and factors were compared to determine if there were factors associated with greater fluctuation.

RESULTS:
122 subjects were analysed. The majority of subjects were male (75.4%) and Chinese (77%). ACD and AXL were shallower/shorter compared with baseline at all postoperative visits, with a mean decrease of 0.11 mm (95% CI 0.07 to 0.15 mm, p<0.01) and 0.16 mm (95%CI 0.11 to 0.20 mm, p<0.01), respectively. Patients with primary open angle glaucoma (POAG) had higher odds of fluctuations in longitudinal measurements of ACD (OR=8.74, p<0.01) and AXL (OR=5.60, p<0.01) compared with patients with primary angle closure glaucoma. For every 1 mm Hg decrease in IOP, ACD and AXL decreased by 0.02 mm (p<0.01) and 0.01 mm (p=0.03), respectively, for POAG patients with emmetropia or mild myopia.

CONCLUSIONS:
Trabeculectomy resulted in a decrease in both ACD and AXL, and these changes were persistent over a period of 5 years.

The Singapore 5-fluorouracil trial: intraocular pressure outcomes at 8 years.

Wong MH1, Husain R, Ang BC, Gazzard G, Foster PJ, Htoon HM, Wong TT, Oen FT, Khaw PT, Seah SK, Aung T.

Abstract
OBJECTIVE:
To report the 8-year outcomes of Asian subjects who underwent trabeculectomy augmented by intraoperative 5-fluorouracil (5-FU) or placebo.

DESIGN:
Retrospective review of a randomized controlled trial.

PARTICIPANTS:
Subjects with primary open-angle or angle-closure glaucoma.

METHODS:
Study subjects were prospectively followed up for 3 years. After the last subject recruited had completed 8 years of follow-up, the charts of all subjects were reviewed to capture data from the year 3 visit onward. Kaplan-Meier survival function with Cox regression was performed to identify risk factors associated with trabeculectomy failure at 8 years.

MAIN OUTCOME MEASURES:
The primary outcome was trabeculectomy failure defined as intraocular pressure (IOP) >21 or <6 mmHg on 2 consecutive occasions after the first 6 weeks after surgery, repeat glaucoma surgery, or loss of light perception. Further end points were defined at IOP levels >17 and >14 mmHg. Secondary outcomes included IOP at 8 years and number of glaucoma medications. Complete success was defined using IOP end points ≤ 21, ≤ 17, or ≤ 14 mmHg at 8 years without medications.

RESULTS:
Of the 243 enrolled subjects, 170 (70.0%) completed 8 years follow-up, 86 in the 5-FU and 84 in the placebo group. There was no significant difference in failure rates at 8 years for the failure definitions of IOP >21 mmHg (11.6% of the 5-FU group vs. 16.7% of the placebo group; P = 1.00), IOP >17 mmHg (23.3% of the 5-FU group vs. 31% of the placebo group; P = 0.78), and IOP >14 mmHg (46.5% of the 5-FU group vs. 58.3% of the placebo group; P = 0.37). Mean IOP at 8 years was 13.7 mmHg in the 5-FU versus 14.4 mmHg in the placebo group (P = 0.24). Mean number of medications was 0.65 drops in the 5-FU versus 0.93 drops in the placebo group (P = 0.06). Complete success with IOP ≤ 21 mmHg at 8 years was achieved in 48 subjects (55.8%) in the 5-FU and 33 subjects (39.3%) in the placebo group (P = 0.09). Absence of bleb microcysts at 1 year, preoperative IOP, and number of bleb needlings performed within the first year were significantly associated with failure.

CONCLUSIONS:
There was no significant difference in IOP between the 5-FU and the placebo group at 8 years.

Efficacy and safety of collagen matrix implants in phacotrabeculectomy and comparison with mitomycin C augmented phacotrabeculectomy at 1 year.

Narayanaswamy A1, Perera SA, Htoon HM, Hoh ST, Seah SK, Wong TT, Aung T.

Abstract
BACKGROUND:
To assess the efficacy and safety of collagen matrix implant (Ologen) in phacotrabeculectomy.

DESIGN:
Prospective, non-randomized, comparative study.

PARTICIPANTS:
Sixty-six Asian patients.

METHODS:
Thirty three consecutive patients underwent phacotrabeculectomy with Ologen implant and intraocular lens implantation, and 33 subjects recruited as controls underwent surgery with mitomycin C augmentation.

MAIN OUTCOME MEASURES:
The primary outcome measure was postoperative intraocular pressure at month 12. Additional postoperative treatments, such as bleb needling, and adverse events were secondary outcomes.

RESULTS:
The overall percentage reduction in intraocular pressure was 13% (95% confidence interval 6.7-19.2) in the Ologen group and 26% (95% confidence interval 14.8-37.9) in the mitomycin C group (P = 0.05). At 1 year after surgery (after adjusting for baseline differences), intraocular pressure decreased by 4.2 mmHg (95% confidence interval 2.8-5.6 mmHg) and 5.6 mmHg (95% confidence interval 4.2-7.0 mmHg), respectively (P = 0.16). Needling with 5-fluorouracil was required more often in the Ologen group (39% vs. 6%; P = 0.003). There was similar frequency (<10%) of adverse events in both groups, and there were no complications directly related to the Ologen implant. The blebs in the mitomycin C group had greater central area (P = 0.005), maximal area (P = 0.01) and height (P = 0.005), and were less vascular (P = 0.023) than the Ologen blebs.

CONCLUSIONS:
At 1 year, the overall performance of Ologen in combined phacotrabeculectomy was suboptimal compared with combined surgery with mitomycin C. Eyes in the Ologen group required more frequent bleb needling procedures.

Initial management of acute primary angle closure: a randomized trial comparing phacoemulsification with laser peripheral iridotomy.

Husain R1, Gazzard G, Aung T, Chen Y, Padmanabhan V, Oen FT, Seah SK, Hoh ST.

Abstract
PURPOSE:
To compare the 2-year efficacy of phacoemulsification and intraocular lens implant (phaco/IOL) with laser peripheral iridotomy (LPI) in the early management of acute primary angle closure (APAC) and coexisting cataract.

DESIGN:
Randomized, controlled trial.

PARTICIPANTS:
We included 37 subjects presenting with APAC who had responded to medical treatment such that intraocular pressure (IOP) was ≤30 mmHg within 24 hours, and had cataract with visual acuity of ≤6/15.

MAIN OUTCOME MEASURES:
The primary outcome measure was failure of IOP control defined as IOP between 22 to 24 mmHg on 2 occasions (readings taken within 1 month of each other) or IOP ≥25 mmHg on 1 occasion, either occurring after week 3. Secondary outcome measures were complications, degree of angle opening, amount of peripheral anterior synechiae, visual acuity, and corneal endothelial cell count (CECC).

METHODS:
Subjects were randomized to receive either LPI or phaco/IOL in the affected eye within 1 week of presentation and were examined at fixed intervals over 24 months. Patients underwent a standardized examination that included Goldmann applanation tonometry, gonioscopy, and CECC measurements. Logistic regression was used to estimate the effect of treatment on failure of IOP control. Time to failure was evaluated using the Kaplan-Meier technique and Cox regression was used to estimate the relative risk of failure.

RESULTS:
There were 18 patients randomized to LPI and 19 to phaco/IOL. The average age of subjects was 66.0±9.0 years and mean IOP after medical treatment was 14.5±6.9 mmHg. The 2-year cumulative survival was 61.1% and 89.5% for the LPI and phaco/IOL groups, respectively (P = 0.034). There was no change in CECC for either group from baseline to month 6. There was 1 postoperative complication in the phaco/IOL group compared with 4 in the LPI group (P = 0.180).

CONCLUSIONS:
Performed within 1 week in patients with APAC and coexisting cataract, phaco/IOL resulted in lower rate of IOP failure at 2 years compared with LPI.

Cataract surgery after trabeculectomy: the effect on trabeculectomy function.
Husain R1, Liang S, Foster PJ, Gazzard G, Bunce C, Chew PT, Oen FT, Khaw PT, Seah SK, Aung T.

Abstract
OBJECTIVE:
To determine whether the timing of cataract surgery after trabeculectomy has an effect on trabeculectomy function in terms of intraocular pressure control.

METHODS:
This was a cohort study nested within a randomized clinical trial. There were 235 participants with glaucoma who had a single previous trabeculectomy augmented with either intraoperative 5-fluorouracil or placebo. Cataract surgery with intraocular lens implantation was performed on participants judged to have significant lens opacity. Cox regression was performed to evaluate the effect of time between trabeculectomy and cataract surgery on the time to trabeculectomy failure, after adjusting for other relevant risk factors. The main outcome measure was time to failure of trabeculectomy, defined as an intraocular pressure of greater than 21 mm Hg.

RESULTS:
Of the 235 participants, 124 (52.7%) underwent subsequent cataract surgery. The median time from trabeculectomy to cataract surgery for these patients was 21.7 months (range, 4.6-81.9 months). The median follow-up period was 60 months (range, 28-84 months) for the cataract surgery group and 48 months (range, 12-84 months) for the non-cataract surgery group. Cox regression showed that the time from trabeculectomy to cataract surgery was significantly associated with time to trabeculectomy failure (hazard ratio, 1.73 [95% CI, 1.05-2.85]; P = .03). The adjusted declining hazard ratios for risk of subsequent trabeculectomy failure when cataract surgery was performed 6 months, 1 year, and 2 years after trabeculectomy were 3.00 (95% CI, 1.11-8.14), 1.73 (95% CI, 1.05-2.85), and 1.32 (95% CI, 1.02-1.69), respectively.

CONCLUSIONS:
Cataract surgery after trabeculectomy increases the risk of trabeculectomy failure, and this risk is increased if the time between trabeculectomy and cataract surgery is shorter.

Central corneal thickness and glaucoma in East Asian people.
Day AC1, Machin D, Aung T, Gazzard G, Husain R, Chew PT, Khaw PT, Seah SK, Foster PJ.

Abstract
PURPOSE:
To examine the association between central corneal thickness (CCT) and glaucoma.

METHODS:
This was a nested case-control study using 1090 subjects from an eye disease population survey in Singapore and 243 participants from a hospital glaucoma surgery clinical trial in Singapore.

RESULTS:
Mean CCT in 938 community subjects was 539 μm ± 32 μm, and in 12 community subjects with primary open angle glaucoma (POAG) the mean CCT was 545 μm ± 38 μm. In the hospital cohort, mean CCT was 552 μm ± 38 μm in 138 patients with POAG and 551 μm ± 33 μm in 105 patients with primary angle closure glaucoma (PACG). No individuals had undergone previous intraocular surgery or had other significant ocular pathology. Regression models showed POAG diagnosis was not associated with CCT (P = 0.42) or age (P = 0.062) in community subjects but was associated with IOP (P = 0.005). Similar analyses for hospital cases showed CCT to be significantly higher in both POAG and PACG (both P = 0.001), but this became nonsignificant after controlling for IOP and age (P = 0.26, POAG; P = 0.08, PACG). Both age (P = 0.043) and IOP (P = 0.001) were highly associated with hospital POAG; only IOP (P = 0.001) was associated with hospital PACG. Further regression analyses for community subjects showed diabetic status and pseudophakia had no significant effect on CCT (P = 0.33 and P = 0.11, respectively).

CONCLUSIONS:
The authors found no evidence to support the previous observation that thinner corneas may be independently associated with POAG or PACG. Age and IOP are significantly associated with CCT, and this should be taken into account by future studies investigating CCT as an independent risk factor for glaucoma diagnosis.

Imaging of blebs after phacotrabeculectomy with Ologen collagen matrix implants.
Boey PY1, Narayanaswamy A, Zheng C, Perera SA, Htoon HM, Tun TA, Seah SK, Wong TT, Aung T.

Abstract
OBJECTIVE:
To analyse blebs of phacotrabeculectomies performed with Ologen collagen implants (ProTop & MediKing, Taipei, Taiwan) and to compare these with blebs of mitomycin C (MMC)–augmented phacotrabeculectomies.

METHODS:
33 participants underwent phacotrabeculectomy with Ologen implants, and 33 controls underwent phacotrabeculectomy with MMC. Blebs were analysed for height and area using anterior segment optical coherence tomography (ASOCT) at 30, 60 and 90 days after surgery and were also graded clinically with the Moorfields bleb grading system (MBGS) 60 days after surgery.

RESULTS:
With ASOCT, there was no difference in mean bleb height at 30 and 60 days, but at 90 days, bleb height was lower in the Ologen group (Ologen vs MMC, 0.74±0.20 vs 1.00±0.28 mm, p<0.001). There was no difference in mean bleb area at 30, 60 or 90 days. Mean reduction in intraocular pressure at 90 days was greater in the MMC group (Ologen vs MMC, 2.18±4.93 vs 8.00 ±7.60 mm Hg, p<0.001). At 90 days, the Ologen implants were visible in ASOCT images in 13 (39.4%) of 33 participants. With the Moorfields bleb grading system at 60 days, there was no difference in maximal bleb area score between the groups, but bleb height score was lower (Ologen vs MMC, 1.53±0.51 vs 1.81±0.59, p=0.05) and central bleb vascularity score was higher in the Ologen group (3.88±0.55 vs 2.91±0.59, p<0.001).

CONCLUSIONS:
Within 3 months of surgery, mean bleb height was lower in the Ologen blebs compared with the MMC blebs. The Ologen implants had not degraded in a third of eyes.

Population prevalence of tilted and torted optic discs among an adult Chinese population in Singapore: the Tanjong Pagar Study.

How AC1, Tan GS, Chan YH, Wong TT, Seah SK, Foster PJ, Aung T.

Abstract
OBJECTIVE:
To determine the prevalence of tilted and torted optic discs and associated risk factors among Chinese adults in Singapore.

METHODS:
As part of a population-based survey, optic disc stereophotographs of both eyes were obtained, and left eyes were analyzed using imaging software. A tilted optic disc was defined as an index of tilt (ratio of minimum to maximum optic disc diameter) less than 0.75. The angle of tilt was defined as the angle between the maximum and vertical optic disc diameter, and optic discs were graded as torted if the angle of tilt exceeded 15 degrees.

RESULTS:
Twenty-six of 739 subjects (3.5%) had tilted optic discs, and 478 (64.7%) had torted optic discs. Myopia was present in 23 of 26 eyes (88.5% [95% confidence interval, 69.9%-97.6%]) with tilted optic discs and in 211 of 661 eyes (31.9% [28.4%-35.6%]) without tilted optic discs (P < .001). On multivariate analysis, myopia (spherical equivalent) was a significant risk factor for tilted optic discs (P < .001). Index of tilt was not associated with corneal astigmatism or with cylindrical refractive error. Seventeen eyes (65.4%) with tilted optic discs had an optic disc morphologic abnormality, but none were glaucomatous.

CONCLUSIONS:
The prevalence of tilted optic discs among this Chinese population was 3.5%. Tilted optic discs were associated with myopia but not with glaucoma.

A randomised crossover study comparing bimatoprost and latanoprost in subjects with primary angle closure glaucoma.
How AC1, Kumar RS, Chen YM, Su DH, Gao H, Oen FT, Ho CL, Seah SK, Aung T.

Abstract
BACKGROUND/AIMS:
To compare the intraocular pressure (IOP) lowering efficacy and side effects of latanoprost 0.005% and bimatoprost 0.03% in subjects with chronic primary angle closure glaucoma (PACG).

METHODS:
This was an observer-masked randomised crossover study of 60 PACG subjects who received either latanoprost or bimatoprost for 6 weeks, after which they were crossed over to the other medication for another 6 weeks. The IOP-reducing effect of the medications was assessed by the reduction in IOP after 6 weeks of treatment compared with baseline.

RESULTS:
Fifty-four subjects (80 eyes) completed the study. Latanoprost reduced IOP (mean (SD)) by 8.4 (3.8) mm Hg and bimatoprost by 8.9 (3.9) mm Hg from a baseline of 25.2 (3.6) mm Hg and 25.2 (3.6) mm Hg respectively (p = 0.23). Adverse events were mild in both groups; however there were twice as many reports of an adverse event in the bimatoprost group (81%) compared with the latanoprost group (40%, p<0.01). Ocular irritation was the most frequently reported adverse event in both groups; 22 subjects (37.9%) treated with bimatoprost experienced ocular hyperaemia as compared with 13 subjects (22.4%) treated with latanoprost (p = 0.11).

CONCLUSIONS:
Bimatoprost once daily was similarly effective in reducing IOP compared with latanoprost once daily in subjects with chronic PACG. Both drugs were well tolerated with mild ocular adverse events.

The singapore 5-Fluorouracil trabeculectomy study: effects on intraocular pressure control and disease progression at 3 years.
Wong TT1, Khaw PT, Aung T, Foster PJ, Htoon HM, Oen FT, Gazzard G, Husain R, Devereux JG, Minassian D, Tan SB, Chew PT, Seah SK.

Abstract
PURPOSE:
To report 3-year results of a randomized, controlled trial comparing the use of a single application of 5-fluorouracil (5-FU) with placebo in trabeculectomy surgery.

DESIGN:
Prospective, randomized, double-blinded treatment trial.

PARTICIPANTS:
Two hundred forty-three Asian patients with primary open-angle or primary angle-closure glaucoma undergoing primary trabeculectomy.

METHODS:
One eye of each patient was randomized to receive either intraoperative 5-FU or normal saline (placebo) during trabeculectomy.

MAIN OUTCOME MEASURES:
Primary outcome measure was the level of intraocular pressure (IOP). Secondary outcomes were progression of visual field loss, rates of adverse events, and interventions after surgery.

RESULTS:
Of the 288 eligible patients, 243 were enrolled and 228 completed 3 years follow-up; 120 patients received 5-FU and 123 received placebo. Trial failure, according to predefined IOP criteria, was lower in the 5-FU group compared with the placebo group, although the difference was only significant with a failure criterion of IOP >17 mmHg (P = 0.0154). There was no significant difference in progression of optic disc and/or visual field loss over 36 months between 5-FU and placebo (relative risk [RR], 0.67; 95% confidence interval [CI], 0.34-1.31; P = 0.239). Uveitis occurred more often in the 5-FU-treated group (14/115 [12%] vs 5/120 [4%]; P = 0.032).

CONCLUSIONS:
This is the first masked, prospective, randomized trial reporting the effect of adjunctive 5-FU in trabeculectomy surgery in an East Asian population. The trial shows that an increased success rate can be achieved for several years after a single intraoperative treatment with 5-FU. We conclude that 5-FU is relatively safe and can be routinely used in low-risk East Asian patients.

Screening for narrow angles in the singapore population: evaluation of new noncontact screening methods.
Lavanya R1, Foster PJ, Sakata LM, Friedman DS, Kashiwagi K, Wong TY, Aung HT, Alfred T, Gao H, Ee AG, Seah SK, Aung T.

Abstract
PURPOSE:
To assess the screening effectiveness of 3 new noncontact devices, the scanning peripheral anterior chamber depth analyzer (SPAC) (Takagi, Nagano, Japan), which measures peripheral anterior chamber depth (ACD); IOLMaster (Carl Zeiss Meditec, Jena, Germany), which measures central ACD; and Visante anterior segment optical coherence tomography (AS-OCT) (Visante, Carl Zeiss Meditec, Dublin, CA), which images the angles, and to compare these instruments with gonioscopy in identifying people with narrow angles (NAs).

DESIGN:
Cross-sectional, observational, community-based study.

PARTICIPANTS:
Phakic subjects aged >or=50 years without ophthalmic symptoms who were recruited from a community polyclinic in Singapore.

METHODS:
All subjects underwent examination with SPAC, IOLMaster, and AS-OCT in the dark by a single operator. Gonioscopy was performed by an ophthalmologist masked to the instruments' findings. The area under the curve (AUC) receiver operating characteristic (ROC) was generated to assess the performance of these tests in detecting people with a NA in either eye.

MAIN OUTCOME MEASURES:
Eyes were classified as having NAs by gonioscopy if the posterior pigmented trabecular meshwork could be seen for <or=2 quadrants of the angle circumference with or without peripheral anterior synechiae.

RESULTS:
A total of 2052 subjects were examined and underwent all 3 tests. The prevalence of a NA in at least 1 eye diagnosed by gonioscopy was 20.4% (422 subjects). The AUC for the SPAC using a numeric grade <5 as a cutoff was 0.83 (95% confidence interval [CI], 0.82-0.85), with a sensitivity of 90.0% (95% CI, 86.8-92.7) and a specificity of 76.6% (95% CI, 74.4-78.6). The AUC for the IOLMaster at an ACD cutoff of <2.87 mm was 0.83 (95% CI, 0.81-0.85), with a sensitivity of 87.7% (95% CI, 84.2-90.7) and a specificity of 77.7% (95% CI, 75.6-79.7). The AUC for the AS-OCT was 0.76 (95% CI, 0.74-0.78), with a sensitivity of 88.4% (95% CI, 84.9-91.3) and a specificity of 62.9% (95% CI, 60.5-65.2).

CONCLUSIONS:
The low specificity found with the SPAC, IOLMaster, and AS-OCT may limit the usefulness of these devices in screening for Nas.

Determinants of angle closure in older Singaporeans.
Lavanya R1, Wong TY, Friedman DS, Aung HT, Alfred T, Gao H, Seah SK, Kashiwagi K, Foster PJ, Aung T.

Abstract
OBJECTIVES:
To investigate systemic and ocular risk factors for angle closure (AC) in older Singaporeans and to determine if these risk factors are different in men vs women and in Chinese vs non-Chinese persons.

METHODS:
A cross-sectional study of 2042 subjects with phakia 50 years or older recruited from a primary care clinic in Singapore. Subjects completed a detailed questionnaire and underwent refraction, biometry, and gonioscopy. Univariate and multivariate analyses were performed to determine risk factors for AC.

RESULTS:
The prevalence of AC among this study population was 19.3% (n = 395); 89.4% (n = 1826) of the study population were Chinese. In univariate analysis, patients with AC were older, female, and of Chinese descent and had shorter axial length, lower body mass index, higher intraocular pressure, and shallower anterior chamber depth. In multivariate analysis, female sex (odds ratio [OR], 1.43; 95% confidence interval [CI], 1.06-1.92; P =.02), Chinese race/ethnicity (OR, 3.58; 95% CI, 2.03-6.29; P < .001), axial length (OR per millimeter increase, 0.69; 95% CI, 0.58-0.81; P<.001), and central anterior chamber depth of less than 2.80 mm vs at least 3.00 mm (OR, 42.5; 95% CI, 27.4-66.2; P<.001) were independently associated with AC.

CONCLUSIONS:
In this community-based study of older Singaporeans, statistically significant independent predictors of AC were female sex, shorter axial length, shallower central anterior chamber depth, and Chinese race/ethnicity. Sex and racial/ethnic differences in the risk of AC were not fully explained by sex and racial/ethnic variations in axial length or anterior chamber depth.

National survey of ophthalmologists in Singapore for the assessment and management of asymptomatic angle closure.
Ang MH1, Baskaran M, Kumar RS, Chew PT, Oen FT, Wong HT, Jap A, Au Eong KG, Seah SK, Aung T.

Abstract
PURPOSE:
Approximately 10% of Chinese people older than 50 years in Singapore have asymptomatic narrow angles [also termed primary angle closure suspects (PACS)]. The aim of this study was to determine the attitudes and practices of ophthalmologists in Singapore regarding the management of these patients.

METHODS:
A nation wide questionnaire-based survey was conducted on all registered, practicing ophthalmologists in Singapore by electronic mail and post. An ophthalmologist was defined as a doctor who had completed at least 3 years of specialist training in ophthalmology and had passed the Master's Degree in Ophthalmology or equivalent examinations. The survey asked the ophthalmologists about the methods and criteria used for the diagnosis of angle closure. It also inquired about the management of PACS and opinions on the effectiveness of prophylactic laser peripheral iridotomy (LPI) in preventing both acute and chronic angle closure.

RESULTS:
A total of 126 out of 158 ophthalmologists responded (79.7% response rate). Of the respondents, 84.9% would advise prophylactic LPI for asymptomatic PACS; 84.9% believed that prophylactic LPI would prevent acute angle closure but only 44% thought that it could prevent the development of glaucomatous optic nerve damage. The preferred method of prophylactic LPI was sequential argon-YAG LPI. In assessing patients for angle closure, 85.4% used gonioscopy, 92.9% assessed anterior chamber depth, and 17.5% performed provocative tests.

CONCLUSIONS:
Ophthalmologists in Singapore vary in the method of assessment of patients with angle closure. Most believe that prophylactic LPI should be performed for asymptomatic PACS.

The morphology of the optic nerve head in the Singaporean Chinese population (the Tanjong Pagar study): part 2--Biometric and systemic associations.
Bourne RR1, Foster PJ, Bunce C, Peto T, Hitchings RA, Khaw PT, Seah SK, Garway-Heath DF.

Abstract
BACKGROUND/AIMS:
To investigate the association of biometric and systemic variables with optic disc characteristics in Chinese Singaporean adults.

METHODS:
Ocular, biometric and medical data including intraocular pressure, refractive error, keratometry, axial length (AL), anterior chamber depth, corneal and lens thickness as well as optic disc data (using planimetry of stereo-photographs) were obtained from 622 normal subjects aged > or = 40 years from the Tanjong Pagar glaucoma survey of Singapore.

RESULTS:
Disc area (DA) was positively associated with AL and height but was unrelated to corneal thickness. Following adjustment for IOP and sex, DA remained positively associated with AL, height and age. Neuroretinal rim area (RA) was also significantly and positively associated with AL and also with height. RA was negatively associated with IOP and was unrelated to blood pressure, history of diabetes, myocardial infarction, stroke or migraine.

CONCLUSIONS:
These data on a Chinese Singaporean population identify height and axial length of the globe as significantly associated with rim area of the disc. These features should be taken into account in statistical assessments of optic nerve head morphometry. This may improve the discriminative ability of image analysis to detect glaucomatous changes. In addition, we identified a statistically significant but small inverse association between rim area and IOP within the normal statistical range.

The morphology of the optic nerve head in the Singaporean Chinese population (the Tanjong Pagar study): part 1--Optic nerve head morphology.
Bourne RR1, Foster PJ, Bunce C, Peto T, Hitchings RA, Khaw PT, Seah SK, Garway-Heath DF.

Abstract
BACKGROUND/AIMS:
To investigate the correlation between optic disc parameters and their association with demographic variables in a Chinese population.

METHODS:
Disc data were obtained from 929 subjects aged > or = 40 years from the Tanjong Pagar glaucoma survey of Singapore, using a novel planimetric method of sequential stereo-photographs. Biometric data (refractive error, keratometry, axial length, anterior chamber depth, lens thickness) were used to calculate ocular magnification. Camera magnification was quantified with a model eye. A "normal" dataset of 622 subjects was generated by exclusion of subjects with abnormal results on psychophysical testing, an occludable angle or an intraocular pressure > 97.5th percentile in either eye.

RESULTS:
Median disc area (DA), cup area (CA), and rim area (RA) were 2.09 (range 1.28-4.01) mm2, 0.69 (0.01-1.90) mm2 and 1.38 (0.82-2.50) mm2, respectively. There was strong evidence of an association between DA and RA (Spearman's rho 0.624, p<0.001). DA and RA were significantly greater in men (median DA = 2.20; range 1.30-3.56; median RA, 1.45; range 0.85-2.30) than women (median DA, 2.00; range 1.28-4.01; median RA, 1.36; range 0.82-2.49, p<0.001). DA increased with age (Spearman's rho 0.115, p = 0.004), while RA was unrelated (rho -0.041; p = 0.308).

CONCLUSIONS:
The morphometric characteristics of optic discs in Chinese Singaporeans are very similar to those described in other groups, with the temporal sector rim having the smallest area. Disc and rim areas vary with sex (men > women). Disc area (but not that of the rim) increases with age.

Assessment of the scleral spur in anterior segment optical coherence tomography images.
Sakata LM1, Lavanya R, Friedman DS, Aung HT, Seah SK, Foster PJ, Aung T.

Abstract
OBJECTIVE:
To assess visibility of the scleral spur in anterior segment optical coherence tomography (AS-OCT) images.

METHODS:
This cross-sectional observational study included 502 participants aged 50 years or older who had no previous ophthalmic problems and were recruited from a community clinic in Singapore. All participants underwent gonioscopy and AS-OCT (Visante; Carl Zeiss Meditec, Dublin, California). Scleral spur location was assessed in AS-OCT images by 2 examiners with glaucoma subspecialty training and was defined as the point where there was an inward protrusion of the sclera with a change in curvature of its inner surface.

RESULTS:
Scleral spur location could be determined in 72% of the images of the right eye. Its location on AS-OCT images was less detectable in quadrants with a closed angle on gonioscopy and also in images obtained in the superior and inferior compared with the nasal and temporal quadrants (64%, 67%, 75%, and 80%, respectively; P < .001).

CONCLUSIONS:
The inability to detect the scleral spur may hamper quantitative analysis of anterior chamber angle parameters that are dependent on the location of this anatomical structure, particularly in the superior and inferior quadrants. New parameters independent of the scleral spur may be useful for detecting eyes at risk of angle closure.

Peripapillary atrophy after acute primary angle closure.
Lee KY1, Rensch F, Aung T, Lim LS, Husain R, Gazzard G, Seah SK, Jonas JB.

Abstract
AIM:
To determine the changes in peripapillary atrophy after episodes of acute primary angle closure (APAC).

METHODS:
Prospective observational study of 40 eyes in 38 patients of predominantly Chinese ethnicity. The mean (SD) intraocular pressure at the time of presentation was 51.7 (12) mm Hg (median, 55 mm Hg) and the mean duration of the symptoms was 37.7 (69.4) hours. A laser iridotomy was undertaken 3.2 (8.4) days after the APAC episode, leading to normalisation of intraocular pressure in all cases. Colour optic disc photographs taken at 2 and 16 weeks after APAC were examined morphometrically. Peripapillary atrophy was divided into alpha and beta zones.

RESULTS:
Comparing measurements at baseline with week 16, the minimum width of the alpha zone (0.013 (0.056) v 0.016 (0.001) arbitrary units; p = 0.23), the maximum width of the alpha zone (1.11 (1.31) v 1.31 (0.79) arbitrary units; p = 0.22), the minimum width of the beta zone (0.030 (0.122) v 0.033 (0.166) arbitrary units; p = 0.93), and the maximum width of the beta zone (0.62 (0.94) v 0.73 (0.98) arbitrary units; p = 0.42) did not vary significantly. The mean cup to disc ratio increased from 0.56 (0.05) to 0.62 (0.07) (p<0.0001) at the end of follow up.

CONCLUSIONS:
The alpha and beta zones of peripapillary atrophy did not enlarge markedly in patients after APAC, despite an enlargement of the optic cup during a follow up of four months.

Comparison of anterior chamber depth measurements using the IOLMaster, scanning peripheral anterior chamber depth analyser, and anterior segment optical coherence tomography.
Lavanya R1, Teo L, Friedman DS, Aung HT, Baskaran M, Gao H, Alfred T, Seah SK, Kashiwagi K, Foster PJ, Aung T.

Abstract
AIM:
To compare anterior chamber depth measurements by three non-contact devices-the IOLMaster, scanning peripheral anterior chamber depth analyser (SPAC), and Visante anterior segment optical coherence tomography (AS-OCT) METHODS: Prospective, cross sectional study of 497 phakic subjects over 50 years of age attending a community clinic in Singapore. Anterior chamber depth of the right eye was measured using all three techniques by the same investigator. Depth measurements were made from the corneal epithelium to the anterior lens surface. The values obtained were compared using Bland-Altman analysis.

RESULTS:
232 men and 265 women were examined (mean (SD) age, 63.4 (7.9) years). Mean anterior chamber depth was 3.08 (0.36) mm with IOLMaster, 3.10 (0.44) mm with SPAC, and 3.14 (0.34) mm with AS-OCT. A significant difference was present between the anterior chamber depth measurements recorded by the three devices (p<0.0001). Mean differences between the measurements were: AS-OCT v IOLMaster, 0.062 (0.007) mm (95% limits of agreement, -0.37 to 0.25 mm) (p<0.0001); AS-OCT v SPAC, 0.035 (0.011) mm (-0.44 to 0.51 mm) (p = 0.0001); SPAC v IOLMaster, 0.027 (0.012) mm (-0.57 to 0.50 mm) (p = 0.027).

CONCLUSIONS:
AS-OCT gave systematically deeper anterior chamber measurements than SPAC and IOL-Master. However, as the differences found were small they are unlikely to be clinically important.

Long-term outcomes in fellow eyes after acute primary angle closure in the contralateral eye.
Friedman DS1, Chew PT, Gazzard G, Ang LP, Lai YF, Quigley HA, Seah SK, Aung T.

Abstract
PURPOSE:
To determine the long-term outcome of the contralateral eye in Asian persons with a unilateral attack of acute primary angle closure (APAC).

DESIGN:
Cross-sectional observational case series.

PARTICIPANTS:
Seventy-nine individuals who were examined from 4 to 10 years after a unilateral episode of APAC at 2 Singapore hospitals.

METHODS:
All subjects underwent a complete eye examination. The optic discs were graded clinically and photographically for the presence of glaucomatous optic neuropathy, and automated visual field tests were assessed for damage. All visual fields and optic nerve photographs (when available) underwent a second evaluation by a masked glaucoma specialist, who assessed whether the changes were compatible with glaucoma.

MAIN OUTCOME MEASURES:
Glaucomatous optic neuropathy, intraocular pressure (IOP), and visual impairment (defined as best-corrected visual acuity of worse than 6/12).

RESULTS:
Ninety of 138 eligible patients (65.2%) with APAC were examined, 79 with unilateral attacks. Subjects were predominantly Chinese (n = 68; 86%). There were 54 females (68%), and mean age was 68.5+/-8.9 years (standard deviation) at the time of APAC, with a mean duration of 6.3+/-1.5 years from the time of the APAC episode to the study examination. The contralateral eyes of 7 patients (8.9%) had definite or probable glaucoma, 2 of whom were felt to have glaucoma in that eye at the time of the attack. Three eyes had markedly cupped optic discs (cup-to-disc ratio > or = 0.9). Thirteen eyes (16.9%) had best-corrected vision worse than 6/12, due to cataract in almost half the cases. Only 1 eye had vision < 6/60, the cause of which was corneal decompensation. One other patient had only a central island remaining with vision of 6/12. Mean IOP of the study participants was 15.7+/-4.7 mmHg, with 6 subjects (7.6%) having undergone trabeculectomy.

CONCLUSIONS:
Definite or probable glaucoma was present at the time of diagnosis in 2 (2.5%) fellow eyes and developed in an additional 5 (6.5%) with a mean follow-up of 6 years. More than 80% of this cohort retained good vision in the contralateral eye, in contrast to the eye that underwent APAC. Unoperated cataract accounted for most of the visual impairment in this group.

Lens opacity, thickness, and position in subjects with acute primary angle closure.
Lim MC1, Lim LS, Gazzard G, Husain R, Chan YH, Seah SK, Aung T.

Abstract
PURPOSE:
To compare lens thickness (LT), lens position (LP), relative lens position (RLP), and degree and type of lens opacity between affected and fellow eyes of subjects with acute primary angle closure (APAC) to identify any differences in lens characteristics that may be contributory to the acute episode. In addition, axial length (AL) and anterior chamber depth (ACD) measurements were evaluated.

METHODS:
Seventy-three study subjects with unilateral APAC were treated with sequential laser iridotomy (LI) in both eyes. Two weeks after LI, ACD, LT, and AL measurements were made in both eyes using ultrasound pachymetry. LP was defined as ACD+1/2LT and RLP as LP/AL. The Lens Opacity Classification III (LOCS III) System was used for grading lens opacity.

RESULTS:
The subjects were 90% Chinese and 63% female. Mean age was 61.0+/-10.9 years. Significant differences between the affected and fellow eyes were found in the ACD (2.11+/-0.35 vs 2.18+/-0.23; P=0.02) and LP (4.61+/-0.47 vs 4.75+/-0.29; P=0.02). Cortical opacity was greater in fellow eyes (0.32+/-0.72 vs 0.53+/-0.95; P=0.02). There was no difference in LT, RLP, or degree of lens opacity in the nuclear and posterior subcapsular regions.

CONCLUSIONS:
Compared with fellow eyes, APAC-affected eyes have shallower ACD, more anterior LP, and less cortical opacity. These differences may be contributory to APAC.

Effect of trabeculectomy on lens opacities in an East Asian population.
Husain R1, Aung T, Gazzard G, Foster PJ, Devereux JG, Chew PT, Oen FT, Khaw PT, Seah SK.

Abstract
OBJECTIVE:
To examine the progression of lens opacity in Asian people after trabeculectomy and determine associated risk factors.

METHODS:
This was an observational case series of 243 people aged 36 to 82 years. Trabeculectomy was performed on 1 eye of each subject. Lens opacity was measured yearly using the Lens Opacification Classification System III. The main outcome measure was worsening of lens opacity defined as an increase of 2 or more Lens Opacification Classification System III units in any of the 3 lens regions, nuclear, cortical, and posterior subcapsular. Risk of progression was evaluated using logistic regression models.

RESULTS:
Data for 177 people were analyzed. One hundred seventeen (66%) of 177 subjects showed progression in opacity in any lens region at 3 years. Seventy-seven (66%) of 117 of those who progressed did so during the first year. Of these, 63 (82%) of 77 had lens opacity in the posterior subcapsular region. Factors associated with progression of posterior-subcapsular lens opacity at 1 year were diabetes (odds ratio, 2.4; 95% confidence interval, 1.0-5.4), use of antiglaucoma medication, dosage of topical steroid postoperatively, and being operated on by a trainee surgeon (odds ratio, 2.3; 95% confidence interval, 1.0-5.2).

CONCLUSIONS:
Trabeculectomy is associated with progression of lens opacity predominantly in the posterior subcapsular region. Modification of risk factors such as postoperative steroid use may delay progression.

Changes in the optic disc after acute primary angle closure.
Shen SY1, Baskaran M, Fong AC, Chan YH, Lim LS, Husain R, Gazzard G, Seah SK, Aung T.

Abstract
PURPOSE:
To evaluate the changes in optic disc morphology in the first 4 months after an episode of acute primary angle closure (APAC) using stereoscopic optic disc photography and computer-assisted planimetry.

DESIGN:
Prospective observational case series.

PARTICIPANTS:
Forty-seven Asian subjects with unilateral APAC who were successfully treated with laser peripheral iridotomy (LPI).

MAIN OUTCOME MEASURES:
Cup-to-disc ratio (CDR) and optic cup and neuroretinal rim areas.

METHODS:
Stereoscopic optic disc photographs were taken 2 and 16 weeks after LPI, and the images were analyzed by computer-assisted planimetry. The overall, quadrantic, and 30 degrees sector areas of the optic disc, CDR, and neuroretinal rim area were analyzed by 2 independent masked graders, and the mean of the readings was used to calculate changes in optic disc parameters.

RESULTS:
The majority of the subjects were female (66%) and Chinese (90%), and the mean age was 67.6+/-11.2 years (range, 40-94). In APAC eyes from week 2 to week 16, the mean CDR increased from 0.56+/-0.05 to 0.59+/-0.03 (P<0.001), and the mean neuroretinal rim area decreased from 1.74+/-0.31 mm2 to 1.59+/-0.27 mm2 (P<0.001). Quadrantic and sector analysis showed preferential loss of neuroretinal rim area at the superotemporal and inferotemporal areas. There was no significant change in optic disc parameters in the fellow eyes over the study period.

CONCLUSIONS:
This study demonstrated changes in optic disc morphology from week 2 to week 16 after an episode of APAC. The pattern of optic nerve damage demonstrated in our study was comparable with that seen in primary open-angle glaucoma and experimental glaucoma models.

Peripapillary retinal nerve fiber layer thickness variations with myopia.
Hoh ST1, Lim MC, Seah SK, Lim AT, Chew SJ, Foster PJ, Aung T.

Abstract
PURPOSE:
To determine the relationship between peripapillary retinal nerve fiber layer (RNFL) thickness and myopia using optical coherence tomography (OCT).

DESIGN:
Prospective observational case series.

METHODS:
One hundred thirty-two young males with myopia (spherical equivalent [SE], -0.50 to -14.25 diopters) underwent ophthalmic examination of one randomly selected eye. Optical coherence tomography (OCT-1, version 4.1) was performed by a single operator using circular scans concentric with the optic disc with scan diameters of 3.40 mm, 4.50 mm, and 1.75 x vertical disc diameter (VDD). For each scan diameter, mean peripapillary RNFL thickness was calculated. Statistical analysis comprised repeated-measurements analysis and Pearson correlation.

RESULTS:
Mean peripapillary RNFL thickness did not correlate with SE for the 3.40-mm (r = -0.11, P = 0.22), 4.50-mm (r = -0.103, P = 0.24), or 1.75xVDD (r = -0.08, P = 0.36) OCT scan diameters. Neither did mean peripapillary RNFL thickness correlate with axial length for the 3.40-mm (r = -0.04, P = 0.62), 4.50-mm (r = 0.03, P=0.75), or 1.75xVDD (r = -0.02, P = 0.78) scan diameters. Mean peripapillary RNFL thicknesses for the 3.40-mm, 4.50-mm, and 1.75xVDD scans were 101.1+/-8.2 microm (95% confidence interval [CI], 99.4-102.8), 78.9+/-8.2 microm (95% CI, 77.5-80.3), and 97.5+/-10.9 microm (95% CI, 95.6-99.4), respectively.

CONCLUSIONS:
Mean peripapillary RNFL thickness did not vary with myopic SE or axial length for any OCT scan diameter investigated. Retinal NFL thickness measurements may be a useful parameter to assess and monitor glaucoma damage in myopic subjects.

Detection of narrow angles and established angle closure in Chinese residents of Singapore: potential screening tests.
Nolan WP1, Aung T, Machin D, Khaw PT, Johnson GJ, Seah SK, Foster PJ.

Abstract
PURPOSE:
To assess the performance of peripheral and central anterior chamber depth (ACD) measurements, and autorefraction, in identifying Chinese people with occludable drainage angles or established primary angle closure.

DESIGN:
Population-based cross-sectional analysis.

METHODS:
Subjects aged 40 years and older were drawn from a representative sample of Chinese Singaporean residents. Limbal chamber depth (LCD) was estimated and central ACD was measured using optical pachymetry and ultrasound. An autorefraction was taken for all subjects. Angle width and the presence of peripheral anterior synechiae were determined by gonioscopy. Receiver operating characteristic curves were generated to show the performance of these tests in detecting occludable angles.

RESULTS:
A total of 1090 subjects were examined. The prevalence of occludable angles was 6.5%. LCD measurement performed best in detecting occludable angles (area under the curve [AUC] 0.904, 95% confidence interval [CI] 0.870, 0.937). Optical pachymetry and ultrasound measurement of ACD performed less well (AUC 0.859 and 0.810, respectively), and autorefraction performed poorly in detecting occludable angles (AUC 0.632). LCD also gave the best performance in detecting primary angle closure (AUC 0.782, 95% CI 0.727, 0.837).

CONCLUSIONS:
Limbal LCD estimation outperforms other methods of measuring ACD as a screening tool for the detection of occludable drainage angles in the Chinese population of Singapore.

Visual acuity after acute primary angle closure and considerations for primary lens extraction.
Tan GS1, Hoh ST, Husain R, Gazzard G, Oen FT, Seah SK, Aung T.

Abstract
BACKGROUND/AIM:
Primary lens extraction has been advocated for acute primary angle closure (APAC), but it is not known if this is warranted in all cases. The aim of this study was to investigate the visual acuity (VA) of APAC eyes shortly after resolution of the acute episode in order to assess the appropriateness of performing such surgery in this condition.

METHODS:
This was a prospective observational case series. As part of a randomised controlled trial comparing phacoemulsification and laser iridotomy, 135 consecutive APAC subjects over a 2 year period underwent subjective refraction and measurement of Snellen VA once the acute episode had resolved with reduction of intraocular pressure (IOP) and improved corneal clarity.

RESULTS:
Subjects were predominantly Chinese (95.6%) and female (79.3%), with a mean age of 63.6 (SD 9.6) years. When assessed 1.7 (2.7) days after presentation, the majority of APAC cases (50.4%) had good VA (6/12 or better), with more than a quarter of cases having VA of 6/7.5 or better. Poor VA was associated with duration of symptoms (p = 0.04, OR = 4.1, 95% CI 1.1 to 15.7) and time taken to resolution of APAC (p = 0.04, OR = 2.2, 95% CI 1.02 to 4.6), but not with sex (p = 0.31), age (p = 0.26), duration from presentation to measurement of visual acuity (p = 0.53), or presenting IOP (p = 0.73).

CONCLUSION:
Within days after APAC, more than half of APAC affected eyes had good VA (6/12 or better). The role of lens extraction in the management of APAC warrants further debate, especially for eyes with good VA.

Iris ischaemic changes and visual outcome after acute primary angle closure.
Loon SC1, Chew PT, Oen FT, Chan YH, Wong HT, Seah SK, Aung T.

Abstract
BACKGROUND:
Ischaemic changes in the iris occur frequently after an episode of acute primary angle closure (APAC). The aim of this study was to investigate the significance of such changes with regards to visual outcome.

METHODS:
Acute primary angle closure cases were treated with medical therapy followed by laser peripheral iridotomy after resolution of the acute episode. Subjects were examined at 1, 4, 8, 12 and 16 weeks post laser peripheral iridotomy. Eyes were examined for signs of iris ischaemic changes (IIC), defined as the presence of iris whorling or stromal atrophy. Iris photographs were also taken at weeks 1, 8 and 16. Subjects requiring glaucoma medication or filtering surgery during the follow-up period were excluded. The visual acuity and visual field (using automated white-on-white threshold perimetry) at week 16 were used in the assessment of visual outcome.

RESULTS:
Sixty-one subjects with APAC completed the study. The majority of subjects were female (82%) and Chinese (92%), and the mean age was 59 +/- 8.8 years. More than half the subjects (52.5%) were found to have developed IIC during the study, 65% of whom already had signs of IIC by the first week. Only 13 subjects (41%) with IIC and 6 subjects (21%) without IIC had an abnormal visual field defect at week 16 (P = 0.09). There was also no difference in visual acuity at week 16, the majority of subjects in both groups having visual acuity of 6/12 or better.

CONCLUSIONS:
The development of iris ischaemic changes after a single episode of APAC may not be associated with an adverse visual outcome.

Cataract progression after prophylactic laser peripheral iridotomy: potential implications for the prevention of glaucoma blindness.
Lim LS1, Husain R, Gazzard G, Seah SK, Aung T.

PURPOSE:
To evaluate changes in lens opacity in the first year after prophylactic laser peripheral iridotomy (LPI) performed in fellow eyes of subjects with acute primary angle closure (APAC).

DESIGN:
Prospective observational case series.

PARTICIPANTS:
Sixty Asian subjects with unilateral APAC.

METHODS:
All fellow eyes underwent prophylactic LPI within the first week of presentation, followed by 1 week of topical steroids. The degree of lens opacity was graded at the slit-lamp examination using the Lens Opacity Classification System III (LOCS III) with standard color photographs as the reference for grading of lens opacity. This was performed 2 weeks, 4 months, and 12 months after LPI. Progression in lens opacity was defined as an increase in LOCS III grade by 2 or more units in any lens region.

MAIN OUTCOME MEASURES:
Lens Opacity Classification Sytem III grades in nuclear, cortical, and posterior subcapsular (PSC) regions.

RESULTS:
Most patients were Chinese (85%) and female (63.3%), with an average age of 61.5 +/- 10.6 years. The mean baseline LOCS grades in the nuclear, cortical, and PSC regions were 3.58 +/- 0.74, 0.57 +/- 1.08, and 0.23 +/- 0.72, respectively. With 12 months of follow-up, 14 of the 60 eyes (23.3%; 95% confidence interval, 16.9-29.7%) showed significant progression in any lens region. Progression in the nuclear, cortical, and PSC regions was documented in 5%, 6.7%, and 16.7% of cases, respectively. By use of logistic regression, the following factors were not found to be significant for cataract progression in any lens region: age, race, gender, history of hypertension or diabetes, presence of peripheral anterior synechiae or angle width at baseline, and total laser energy delivered.

CONCLUSIONS:
In fellow eyes of APAC, prophylactic LPI is complicated by significant cataract progression, mainly in the posterior subcapsular region. These findings may have implications for the role of prophylactic LPI in the prevention of angle-closure blindness.

Use of surodex in phacotrabeculectomy surgery.
Seah SK1, Husain R, Gazzard G, Lim MC, Hoh ST, Oen FT, Aung T.

Abstract
PURPOSE:
To evaluate the use of Surodex (Oculex Pharmaceuticals, Sunnyvale, California) a drug delivery system incorporating 60 micrograms of dexamethasone in a pellet, in phacotrabeculectomy surgery.

DESIGN:
Nonrandomized, prospective, interventional case series.

METHODS:
Phacotrabeculectomy was performed on 37 Asian subjects with primary open-angle glaucoma (POAG) using a standardized technique. All subjects received a Surodex pellet underneath the scleral flap. Results were compared with those of 31 POAG subjects who had undergone phacotrabeculectomy augmented with 50 mg/ml of intraoperative 5-fluorouracil (5-FU) during the same period.

RESULTS:
Mean follow-up in months was 19.7 +/- 7.9 and 22.1 +/- 6.2 for the Surodex and 5-FU groups, respectively (P = .29). There was a 20.1% decrease in intraocular pressure in the Surodex group compared with 28.5% decrease in the 5-FU group (P = .6). Postoperative complications occurred in three cases (8.1%) and six cases (19.3%), respectively (P = .04).

CONCLUSIONS:
Combined phacotrabeculectomy surgery augmented by intra-scleral placement of Surodex results in good control of IOP and a low incidence of complications.

Anterior chamber depth and the risk of primary angle closure in 2 East Asian populations.
Aung T1, Nolan WP, Machin D, Seah SK, Baasanhu J, Khaw PT, Johnson GJ, Foster PJ.

Abstract
OBJECTIVE:
To evaluate the risk of peripheral anterior synechiae (PAS) and glaucomatous optic neuropathy attributable to primary angle closure at varying anterior chamber depths (ACDs) in two East Asian populations.

METHODS:
Participants 40 years and older were from 2 population-based glaucoma surveys in Mongolia and Singapore. Central ACD was measured by optical pachymetry. Presence of PAS was determined by dynamic gonioscopy. Cases with secondary PAS were excluded. Glaucomatous optic neuropathy was diagnosed in subjects with structural and functional evidence of glaucoma.

RESULTS:
A total of 2032 subjects, consisting of 942 Mongolians and 1090 Chinese Singaporeans, were included in this study. A logistic model of the relationship between ACD and PAS among Singaporeans showed a consistent, incremental increase in PAS across the entire range of ACD. In deeper anterior chambers the rate of PAS exceeded that seen in Mongolians. In Mongolians, there was a clear threshold for ACD (2.4 mm) at or above which PAS were very uncommon. With ACD less than 2.4 mm, the rate of PAS rose rapidly to overtake that seen in Singaporeans.

CONCLUSIONS:
Shallow anterior chambers are a significant risk factor for angle closure in East Asians, although the nature of the association is specific to the individual population. There was a trend toward higher rates of glaucomatous optic neuropathy in people with the shallowest anterior chambers.

Molecular analysis of the myocilin gene in Chinese subjects with chronic primary-angle closure glaucoma.
Aung T1, Yong VH, Chew PT, Seah SK, Gazzard G, Foster PJ, Vithana EN.

Abstract
PURPOSE:
Mutations in the myocilin (MYOC) gene have been implicated in juvenile as well as late-onset primary open-angle glaucoma (POAG). Overall, MYOC mutations account for 3% to 5% of cases of POAG worldwide, making it the most significant gene identified so far in glaucoma. Although there are some similarities in the phenotype of POAG and in particular chronic primary angle-closure glaucoma (PACG), little is known about the role of MYOC in the causation of PACG. To address this, the MYOC gene was screened in a cohort of 106 patients with chronic PACG.

METHODS:
Genomic DNA was extracted from leukocytes of the peripheral blood and exons 1 to 3 of the MYOC gene were PCR amplified and subjected to bidirectional sequencing and analysis.

RESULTS:
One hundred six patients with chronic PACG of Chinese ethnicity were studied. Sequencing of the MYOC gene in these patients revealed eight sequence variants. Of these, one was a nonsense change, three were missense changes, two were synonymous codon changes, and two were changes in noncoding sequences. These included the Arg46Stop and Thr353Ile mutations, which have been reported in individuals with POAG. However, all the sequence alterations identified have been found in normal Chinese subjects.

CONCLUSIONS:
The results of this study do not support a role for MYOC mutations in the pathogenesis of chronic PACG in the Chinese.

Optic disk ovality as an index of tilt and its relationship to myopia and perimetry.
Tay E1, Seah SK, Chan SP, Lim AT, Chew SJ, Foster PJ, Aung T.

Abstract
PURPOSE:
To examine the association of optic disk ovality with myopic refractive error, axial length, and the visual field.

DESIGN:
Prospective observational case series.

METHODS:
The study included 150 randomly recruited male subjects with myopia. In all cases, one eye was randomly selected, and subjective refraction, slit-lamp examination, applanation tonometry, gonioscopy, A-scan ultrasonography, funduscopy, and color optic disk stereo photography were performed. Disk ovality was assessed using the ratio of minimum to maximum disk diameter (index of tilt). A ratio of < or = 0.8 was considered as significant disk tilt. Visual fields were tested using static automated threshold perimetry with two methods of optical correction: trial lenses and contact lenses.

RESULTS:
Of the total sample, 137 subjects completed the study. Mean age was 21.2 +/- 1.1 year, and mean spherical equivalent was -6.36 +/- 3.56 diopters. Mean ovality ratio was 0.83 +/- 0.09; 55 subjects (40.2%) had significant tilted optic disks. Greater optic disk ovality (tilt) correlated with greater myopia (P = .009) and longer axial length (P = .009); 95.6% of subjects had normal visual fields with both methods of optical correction. Using multiple linear regression analysis, greater tilt was independently related to a higher mean defect on testing with trial lenses (P < .01).

CONCLUSIONS:
Increased optic disk tilt was associated with higher myopia and reduced sensitivity on field testing. These factors are important in the assessment of glaucoma in patients with myopia.

Use of optical coherence tomography to assess variations in macular retinal thickness in myopia.
Lim MC1, Hoh ST, Foster PJ, Lim TH, Chew SJ, Seah SK, Aung T.

Abstract
PURPOSE:
To investigate the variation in macular retinal thickness in otherwise normal young Asian myopic subjects by using optical coherence tomography (OCT).

METHODS:
One hundred thirty ophthalmically normal men 19 to 24 years of age with myopia (spherical equivalent, -0.25 to -14.25 D) underwent examination of one randomly selected eye. Visual acuity, refraction, slit lamp examination, applanation tonometry, gonioscopy, A-scan ultrasound, fundus examination, visual field testing, and optic disc photography were performed. Exclusion criteria were visual acuity worse than 20/30, previous intraocular surgery, intraocular pressure >21 mm Hg, or other ocular diseases. Three horizontal transfixation and three vertical transfixation OCT scans (ver.4.1; Carl Zeiss Meditec, Dublin, CA) of 6 mm each were conducted on each eye by a single operator. Neurosensory retinal thicknesses at 100 points along each scan were measured, and the overall average, maximum, and minimum retinal thicknesses were analyzed by simple linear regression and analysis of variance.

RESULTS:
The average macular retinal thickness (overall) was 230.9 +/- 10.5 microm and was not significantly related to the degree of myopia. The mean maximum retinal thickness (at the parafovea) was 278.4 +/- 13.0 microm, and correlated negatively with axial length (P = 0.03). The mean minimum retinal thickness (at the foveola) was 141.1 +/- 19.1 microm, and this was positively correlated with axial length (P = 0.015) and spherical equivalent (P = 0.0002). The retina was thicker at the superior and nasal parafovea compared to the inferior or temporal parafovea.

CONCLUSIONS:
Average retinal thickness of the macula does not vary with myopia. However, the parafovea was thinner and the fovea thicker with myopia.

Choroidal expansion as a mechanism for acute primary angle closure: an investigation into the change of biometric parameters in the first 2 weeks.
Yang M1, Aung T, Husain R, Chan YH, Lim LS, Seah SK, Gazzard G.

Abstract
BACKGROUND/AIM:
Choroidal expansion with anterior movement of the lens was recently proposed as a mechanism for acute primary angle closure (APAC). The aim of this study was to compare the biometric parameters, central anterior chamber depth, limbal chamber depth, lens thickness, and lens position, within 24 hours of presentation and 2 weeks later in eyes with APAC.

METHODS:
This was a prospective observational case series of 41 subjects with APAC. Subjects who presented with APAC were treated with medical therapy followed by laser iridotomy (LI) in both eyes once the acute attack was broken. Ocular biometry was performed in affected and fellow eyes before LI (baseline) and then 2 weeks later. Optical pachymetry was used to measure central anterior chamber depth (ACD) and the limbal chamber depth (LCD) was graded at the slit lamp. A-scan ultrasound was used to measure lens thickness (LT) and axial length (AL). Lens position (LP) was defined as ACD +(1/2)LT.

RESULTS:
The majority of subjects were Chinese (83%) and female (61%), and the mean age was 60.4 (SD 10.3) years. In affected eyes, the ACD was 1.81 (0.29) mm before and 1.80 (0.28) mm 2 weeks after LI (p = 0.63), while in fellow eyes, the ACD was 1.83 (0.29) mm and 1.81 (0.38) mm, respectively (p = 0.21). There was no significant change in lens position, relative lens position, or axial length in both affected and fellow eyes over the 2 weeks.

CONCLUSIONS:
There was no change observed in central anterior chamber depth, lens thickness, or lens position at the time of the acute attack compared to 2 weeks later in both APAC affected and fellow eyes. The findings do not support the hypothesis of lens movement due to choroidal expansion in APAC.

Changes in retinal nerve fiber layer thickness after acute primary angle closure.
Aung T1, Husain R, Gazzard G, Chan YH, Devereux JG, Hoh ST, Seah SK.

Abstract
PURPOSE:
To evaluate the changes in retinal nerve fiber layer (RNFL) thickness in the first 16 weeks after acute primary angle closure (APAC) using scanning laser polarimetry (SLP).

DESIGN:
Prospective, observational case series.

PARTICIPANTS:
Thirty-seven Asian subjects with APAC.

METHODS:
For all cases, APAC had resolved after treatment, and the study was conducted during the follow-up period after the acute episode. Using the GDx Nerve Fiber Analyzer (Laser Diagnostic Technologies, San Diego, CA), the RNFL was assessed in both eyes 2 weeks after APAC, and again after 16 weeks. The SLP parameters were compared between week 2 and week 16 within affected and fellow eyes. A multiple logistic regression analysis was carried out to analyze factors likely to influence RNFL outcome.

MAIN OUTCOME MEASURES:
Superior and inferior average RNFL thickness.

RESULTS:
The mean age of study subjects was 60.1+/-10.3 years (range, 46-91 years), and most subjects were female (68%) and Chinese (86%). In APAC eyes, the superior average RNFL thickness decreased from 63.8+/-13.6 microm to 61.4+/-11.2 microm (P = 0.04) and the inferior average RNFL thickness decreased from 69.5+/-14.4 microm to 66.3+/-12.6 microm (P = 0.005). There was also a decrease in inferior ratio (P = 0.008) and ellipse modulation (P = 0.02). In the fellow eyes, there was no difference found between week 2 and week 16 for any of the SLP parameters studied. Logistic regression analysis showed no significant association between developing a 10% reduction in either superior or inferior RNFL thickness with age, gender, history of ischemic risk factors, duration of symptoms during APAC, the level of presenting intraocular pressure (IOP), or the development of a rise in IOP between study visits.

CONCLUSIONS:
After an episode of APAC, superior and inferior average RNFL thickness was found to decrease significantly from week 2 to week 16.

Acute primary angle closure: configuration of the drainage angle in the first year after laser peripheral iridotomy.
Lim LS1, Aung T, Husain R, Wu YJ, Gazzard G, Seah SK.

Abstract
PURPOSE:
To evaluate the changes in the configuration of the drainage angle in the first year after acute primary angle closure (APAC).

DESIGN:
Prospective observational case series.

PARTICIPANTS:
Forty-four Asian subjects with APAC.

METHODS:
Acute primary angle closure cases were treated with medical therapy followed by laser peripheral iridotomy (LPI). Static and dynamic gonioscopies were performed in APAC-affected and fellow eyes before LPI (baseline) and then at 2 weeks, 4 months, and 12 months after presentation. The angles were graded in each quadrant according to the Shaffer scheme, and the number of clock hours of peripheral anterior synechiae (PAS) was recorded. Patients who underwent intraocular surgery at any point during follow-up were excluded from the study. Intraocular pressure (IOP) and medical treatment were documented at each visit, and gonioscopic changes were correlated with the development of elevation in IOP requiring medical treatment.

MAIN OUTCOME MEASURES:
Average Shaffer grade and the number of clock hours of PAS.

RESULTS:
The majority of subjects were Chinese (84%) and female (64%), and the mean age was 60.2+/-10.7 years. At presentation, 73% of both affected and fellow eyes had very narrow angles (average Shaffer grade < or = 1), with affected eyes having more extensive PAS (P<0.001), a third of whom had > or =8 clock hours of PAS. In APAC eyes, there was a significant increase in angle width from baseline to 2 weeks after LPI (P = 0.045), but no change in angle width subsequently. Fellow eyes showed a widening of the angle between baseline and week 2 (P = 0.01) and from week 2 to month 4 (P = 0.001). There was no significant change in PAS in either affected or fellow eyes over the 12 months of follow-up. Of the 44 subjects, 19 (41.3%) subsequently developed IOP elevation during follow-up that required treatment. However, there was no difference in angle width or amount of PAS between eyes with and without a subsequent rise in IOP, and the angle configuration did not change significantly in either group over 1 year.

CONCLUSION:
In Asian eyes with APAC, the angle widened in the first 2 weeks after LPI, but did not change thereafter over 1 year, and the amount of PAS remained stable throughout. The results indicate the effectiveness of LPI in preventing progressive closure of the angle in the first year after APAC.

Long-term outcomes in asians after acute primary angle closure.
Aung T1, Friedman DS, Chew PT, Ang LP, Gazzard G, Lai YF, Yip L, Lai H, Quigley H, Seah SK.

Abstract
PURPOSE:
To determine the long-term outcome of Asian eyes with an acute attack of primary angle closure (APAC) and to identify risk factors at presentation associated with the development of glaucomatous optic nerve damage.

DESIGN:
Cross-sectional observational case series.

PARTICIPANTS:
Ninety individuals who were initially seen with APAC 4 to 10 years previously at 2 Singapore hospitals.

METHODS:
All subjects underwent a complete eye examination, including visual acuity, visual field testing, dilated eye examination, and optic nerve head photography. The optic discs were judged clinically and photographically as to whether there was glaucomatous optic neuropathy present, and visual fields were assessed for corresponding visual field loss. All visual fields and optic nerve photographs underwent a second evaluation by an experienced, but masked, glaucoma specialist, who assessed whether the changes were compatible with glaucoma.

MAIN OUTCOME MEASURES:
The main outcome measures were blindness (defined as best-corrected visual acuity worse than 6/60 and/or central visual field of less than 20 degrees in the attack eye) and glaucomatous optic neuropathy (GON).

RESULTS:
A total of 90 of 170 eligible subjects (65.2%) were examined. All subjects were Asian and were predominantly Chinese (78 subjects [86.7%]). There were 61 females (67.8%), and the age of the subjects was 62.0+/-9.0 years (mean +/- standard deviation) at the time of APAC, with a mean duration of 6.3+/-1.5 years from the time of the APAC episode to the study examination. Sixteen (17.8%) subjects were blind in the attack eye; half of the cases of blindness were caused by glaucoma. Forty-three subjects (47.8%) had GON, with 13 eyes (15.5%) having markedly cupped optic discs (cup-to-disc ratio >0.9). Thirty-eight eyes (58%) had best-corrected vision worse than 6/9, with cataract responsible for close to half the cases of poor vision. There were no identifiable risk factors related to the APAC episode that were significantly associated with the presence of GON.

CONCLUSIONS:
Several years after being seen with APAC, 17.8% of subjects examined were blind in the attack eye, and almost half had glaucomatous optic nerve damage. Vision was also reduced in a large number of individuals, largely from unoperated cataract. Subjects with APAC would benefit from regular follow-up to monitor for visual field decline and glaucoma development.

Interocular asymmetry of visual field defects in primary open angle glaucoma and primary angle-closure glaucoma.
Wang JC1, Gazzard G, Foster PJ, Devereux JG, Oen FT, Chew PT, Khaw PT, Seah SK.

Abstract
AIM:
To compare the interocular asymmetry in visual field loss of patients with primary open-angle (POAG) and primary angle-closure glaucoma (PACG).

METHODS:
Subjects entering a prospective, randomised, controlled trial of intraoperative 5-fluorouracil in glaucoma surgery in Singapore were included. Preoperative visual field testing was performed using automated white-on-white perimetry (24-2 test pattern, threshold program, Mk II, Model 750, Zeiss-Humphrey, San Leandro, CA, USA). A minimum of two tests were required with mean deviation within 2 dB on two tests, fixation losses <20%, false positives <33%, and false negatives <33%. The second field was scored using AGIS II criteria and the 'mean asymmetry score' defined as the mean difference between eyes for both AGIS scores and global indices.

RESULTS:
In 230 subjects assessed (128 POAG, 102 PACG), mean interocular asymmetry of visual field loss was greater for the PACG group. The mean AGIS asymmetry scores for total (PACG=9.21+/-6.87 vs POAG=6.48+/-5.58, P=0.001), superior (PACG=4.31+/-3.39 vs POAG=3.35+/-3.13, P=0.035), and inferior (PACG=4.43+/-3.31 vs POAG=2.64+/-2.77, P<0.0001) areas and mean deviation (MD) asymmetry scores (PACG=6.89+/-13.22 vs POAG=1.66+/-16.97, P=0.012) were all significantly different. Interocular correlation of visual field loss for POAG was significant; total AGIS, r=0.27 (P=0.003), superior field AGIS, r=0.24 (P=0.008), inferior field AGIS, r=0.34 (P=0.0001), and MD, r=0.27 (P=0.003). In PACG, there was no significant correlation between eyes; total AGIS, r=-0.02 (P=0.85), superior field AGIS, r=-0.02 (P=0.82), inferior field AGIS, r=-0.17 (P=0.87), and MD, r=0.015 (P=0.89).

CONCLUSION:
There was a greater asymmetry of visual field loss between eyes, as measured by AGIS scores and MD, in PACG than that in POAG.

Defining "occludable" angles in population surveys: drainage angle width, peripheral anterior synechiae, and glaucomatous optic neuropathy in east Asian people.
Foster PJ1, Aung T, Nolan WP, Machin D, Baasanhu J, Khaw PT, Alsbirk PH, Lee PS, Seah SK, Johnson GJ.

Abstract
BACKGROUND:
Aim: A current consensus in epidemiological studies of primary angle closure (PAC) is to diagnose the condition only if the posterior (usually pigmented) trabecular meshwork is seen for less than 90 degrees of the angle circumference, termed an "occludable angle." The authors sought to assess the validity of this epidemiological classification by exploring the relation between drainage angle width, peripheral anterior synechiae (PAS) and glaucomatous optic neuropathy (GON).

METHODS:
918 Mongolians and 995 Chinese Singaporeans, both groups aged 40 years and older were examined in two population based surveys. Gonioscopic angle width was graded in five categories (0 = closed to 4 = wide open) according the scheme described by Shaffer. Cases with secondary PAS were excluded.

RESULTS:
The rate of PAS was between 0.3% and 1.7% in people with wide angles (grades 3 and 4). In those with grade 2 angles, PAS were seen in between 8% of eyes. In eyes with grade 1 angles, the rate rose to 17% in Chinese Singaporeans, and 31% in Mongolians. The odds of PAS were higher in people with narrower angles. However, there was a greater absolute number of people with PAS whose drainage angles were classified as "not occludable" than those classified "occludable."

CONCLUSIONS:
The traditional view that primary angle closure becomes a significant possibility in drainage angles of < or = grade 2 (approximately 20 degrees ) is valid in east Asians. The definition of an "occludable" angle examined here excludes many people with PAS. This probably serves to underemphasise the role of PAC in population surveys of glaucoma prevalence in Asian people.

Effect of cataract extraction and intraocular lens implantation on nerve fibre layer thickness measurements by scanning laser polarimeter (GDx) in glaucoma patients.
Gazzard G1, Foster PJ, Devereux JG, Oen F, Chew PT, Khaw PT, Seah SK.

Abstract
PURPOSE:
To assess the influence of visually significant cataract on the measurement of nerve fibre layer thickness by scanning laser polarimetry (GDx) in glaucoma patients undergoing phacoemulsification cataract extraction.

METHOD AND SUBJECTS:
All subjects with primary glaucoma participating in a prospective trial of glaucoma surgery who subsequently underwent cataract extraction were eligible. A single trained observer using the GDx nerve fibre layer analyser (LDT) performed pre- and post-operative measurements of nerve fibre layer thickness (NFLT). NFLT parameters, best-corrected LogMAR visual acuity, and automated visual fields were assessed before and after phacoemulsification cataract extraction with implantation of an acrylic intraocular lens.

RESULTS:
A total of 49 subjects were assessed: 22 (45%) had POAG and 29 (55%) PACG; all were Asian (36 (73%) were Chinese), with mean age 67.1 (+/-7.6 SD) and mean 'LOCS III' lens opacity grading 11.4 (+/-3.1 SD). Visual acuity significantly improved (mean LogMAR 0.5 vs 0.15, P<0.0001). Corrected pattern standard deviation (6.1 vs 6.4, P=0.2) and mean deviation (-17.7 dB vs -17.0 P=0.91) were little changed after cataract removal. Pseudo-phakic measurements of NFLT were significantly different from pre-op values. Measures of absolute thickness (including the average thickness, ellipse, ellipse average, superior and inferior averages, superior integral) were significantly greater than preoperative values (all P<0.01), whereas ratios and measures of symmetry (symmetry, superior/nasal) were unchanged (all P>0.1) and 'the number' was smaller (P=0.04). Differences in measured NFLT were most strongly correlated with posterior subcapsular cataract (average thickness, P=0.01).

CONCLUSIONS:
Removal of cataract resulted in greater absolute measurements of NFLT but ratio values were unchanged. Scanning laser polarimetry measurements can change significantly after cataract extraction. New baseline measurements may be required.

Randomised controlled trial comparing the effect of brimonidine and timolol on visual field loss after acute primary angle closure.
Aung T1, Oen FT, Wong HT, Chan YH, Khoo BK, Liu YP, Ho CL, See J, Thean LH, Viswanathan AC, Seah SK, Chew PT.

Abstract
AIM:
To compare the effect of brimonidine and timolol in reducing visual field loss in patients with acute primary angle closure (APAC).

METHODS:
In addition to standard acute medical treatment, patients presenting with APAC were randomised to either brimonidine 0.2% or timolol 0.5% upon diagnosis, then twice daily for 4 weeks. After laser peripheral iridotomy (LPI), subjects underwent three baseline perimetry tests during the first week, and then at weeks 4, 8, 12, and 16. Pointwise linear regression analysis was applied to the field series of each of these subjects starting with the third test (total of five tests per subject). Progression was defined as a significant regression slope (p<0.05) showing 1 dB per year or more of sensitivity loss at the same test location in the series. Patients were also compared for prevalence of abnormal fields at 16 weeks, which was defined as an abnormal glaucoma hemifield test result and/or corrected pattern standard deviation outside the 95% confidence limits.

RESULTS:
59 subjects (31 in the brimonidine group; 28 in the timolol group) completed the study. There were 47 females (79.7%), the majority of subjects (94.9%) were Chinese and the mean age was 59.2 (SD 7.2) years. There were no significant differences between the two groups with respect to demographic features, presenting intraocular pressure (IOP), duration of symptoms, time from presentation to LPI, or mean IOP at each study visit. Over the 16 week study period, despite adequate statistical power, no difference was found between groups in terms of the number of patients with progressing locations, the mean number of progressing locations per subject, or the mean slope of the progressing locations. Nine (29%) subjects in the brimonidine group and 10 (35.7%) in the timolol group were found to have significant visual field defects at 16 weeks (p = 0.58). 15 out of these 19 subjects (78.9%) already had these visual field defects in the first week.

CONCLUSIONS:
In the first 16 weeks after APAC, there was no difference in the prevalence of visual field defects or rate of visual field progression between brimonidine and timolol treated groups.

Combined phacoemulsification, intraocular lens implantation and trabeculectomy for chronic angle closure glaucoma.
Tow SL1, Aung T, Oen FT, Seah SK.

Abstract
PURPOSE:
To investigate the results of combined phacoemulsification, intraocular lens implantation and trabeculectomy in Asian patients with chronic angle closure glaucoma (CACG).

METHODS:
This was a retrospective non-comparative case series of 55 consecutive patients (57 eyes) who underwent phacoemulsification, posterior chamber intraocular lens implantation and trabeculectomy for CACG at the Singapore National Eye Centre between 1997-1998. The surgical outcome was assessed in terms of intraocular pressure (IOP), the incidence of complications and the visual acuity at last follow-up. Success was defined as final IOP < or = 21 mmHg without medication and qualified success as final IOP < or = 21 mmHg with medication. Patients with final IOP > 21 mmHg who required further glaucoma surgery, lost light perception or became pthisical, were classified as failures. The eyes were further categorized into two groups according to whether single-site or separate-site surgery was performed. The outcome was also compared among eyes in which per-operative antimetabolites were applied to the trabeculectomy site and those without antimetabolites.

RESULTS:
The mean follow up was 22.0 +/- 5.6 months (mean +/- SD). Success was achieved in 46 (81%) eyes, qualified success in 10 (17%) eyes, and failure in 1 (2%) eye. In terms of IOP outcome, the success rate was similar in the two surgical groups (single-site or separate-site). There was no significant difference in IOP outcome among eyes in which per-operative antimetabolites were used and eyes with no per-operative antimetabolites use. Forty-one eyes (72%) had 6/12 or better vision. There were no cases of intraoperative complications and the incidence of postoperative complications was low.

CONCLUSIONS:
Combined phacoemulsification, intraocular lens implantation and trabeculectomy is associated with good intraocular pressure control and visual outcome in patients with CACG.

Determinants of intraocular pressure and its association with glaucomatous optic neuropathy in Chinese Singaporeans: the Tanjong Pagar Study.
Foster PJ1, Machin D, Wong TY, Ng TP, Kirwan JF, Johnson GJ, Khaw PT, Seah SK.

Abstract
PURPOSE:
To examine the relationship between intraocular pressure (IOP), anthropomorphic, demographic, socioeconomic, systemic, and ocular factors and glaucomatous optic neuropathy (GON) in Chinese people.

METHODS:
Chinese people (n = 2000), aged 40 to 79 years, were selected from the Singapore electoral register. Of the 1717 considered eligible for examination, 1232 participated, representing a response rate of 71.8%. IOP was estimated with Goldmann applanation tonometry. The drainage angle was assessed with static and dynamic gonioscopy. The optic nerve was examined at high magnification through a dilated pupil with a fundus contact lens or a +78-D lens. Static automated visual field testing was performed on subjects with suspected glaucoma. GON was diagnosed on the basis of structural and functional abnormalities of the optic nerve.

RESULTS:
The main independent determinants of higher IOP were higher systolic blood pressure (P < 0.001), quadrants of any peripheral anterior synechiae (PAS, P = 0.02) and width of the drainage angle (P = 0.049). A 100- micro m increase in corneal thickness was associated with an increase in mean IOP of 1.5 to 1.8 mm Hg (P < 0.001). Odds of GON increased 1.2 times per 1-mm Hg increase in screening IOP. A clear association between corneal thickness and GON was not identified.

CONCLUSIONS:
Clinical IOP estimates are related to systolic blood pressure and corneal thickness. Variation in IOP with angle width may suggest that trabecular compaction significantly contributes to causes of the increase in IOP, independent of angle-closure. GON is an IOP-related phenomenon among Chinese Singaporeans.

Risk factors for nuclear, cortical and posterior subcapsular cataracts in the Chinese population of Singapore: the Tanjong Pagar Survey.
Foster PJ1, Wong TY, Machin D, Johnson GJ, Seah SK.

Abstract
AIM:
To describe risk factors for nuclear, cortical, and posterior subcapsular (PSC) cataracts in Chinese Singaporeans.

METHODS:
A population based cross sectional study was carried out on ethnic Chinese men and women aged 40-81 years. A stratified, clustered, disproportionate (more weights to older people), random sampling procedure was used to initially select 2000 Chinese names of those aged 40-79 years from the 1996 electoral register in the Tanjong Pagar district in Singapore. Eligible subjects (n = 1717) were invited for a standardised ocular examination and interview at a centralised clinic, following which an abbreviated examination was conducted for non-respondents in their homes. Cataract was graded clinically using to the Lens Opacity Classification System (LOCS) III system. The main outcome measures were adjusted odds ratio for risk factors for specific cataract types (nuclear, cortical and PSC), any cataract and cataract surgery, examined in multiple logistic regression models.

RESULTS:
Out of the 1232 (71.8%) examined, 1206 (70.2%) provided lens data for this analysis. Increasing age was associated with all cataract types, any cataract, and cataract surgery. There was no significant sex difference in presence of any cataract, specific cataract types or cataract surgery. After controlling for age, sex, and other factors, diabetes was associated with cortical cataract (3.1; 95% CI: 1.6 to 6.1), PSC cataract (2.2; 95% CI 1.2 to 4.1), any cataract (2.0; 95% CI: 0.9 to 4.5), and cataract surgery (2.3; 95% CI: 1.3 to 4.1). Lower body mass index was associated with cortical cataract (1.8; 95% CI: 1.1 to 2.9; lowest versus highest quintile) and any cataract (2.3; 95% CI: 1.3 to 4.0). Current cigarette smoking was associated with nuclear cataract (1.7, 95% CI: 1.0 to 2.9; more than 10 cigarettes per day versus none). A non-professional occupation was associated with nuclear cataract (2.9; 95% CI: 1.5 to 5.8; for production or machine operators and 2.6; 95% CI: 1.2 to 5.5; for labourers or agricultural workers, both versus professionals). Lower education was associated with nuclear cataract (2.3; 95% CI: 1.0 to 5.2, none versus tertiary), while lower household income was associated with PSC cataract (4.7, 95% CI: 1.1 to 20.0; income <S$2000 versus >S$4000).

CONCLUSIONS:
Age related cataracts are associated with a variety of risk factors among Chinese people in Singapore, similar to those reported in European, Indian, and African derived populations. These data support common aetiological mechanisms for age related cataracts, irrespective of ethnic origin.

Intermediate-term outcome of Baerveldt glaucoma implants in Asian eyes.
Seah SK1, Gazzard G, Aung T.

Abstract
PURPOSE:
To determine the intermediate-term efficacy and safety of Baerveldt glaucoma implants in Asian eyes with complicated glaucoma.

DESIGN:
Retrospective, nonrandomized, comparative trial.

PARTICIPANTS:
One hundred twenty-four Asian patients (124 eyes) with complicated glaucoma.

INTERVENTION:
Implantation of 54 250-mm(2) and 70 350-mm(2) Baerveldt glaucoma drainage implants at Singapore National Eye Center from 1994 through 1999.

MAIN OUTCOME MEASURES:
Intraocular pressure, number of glaucoma medications, and complications.

RESULTS:
The mean follow-up period was 33.4 +/- 14.4 months (mean +/- SD; range, 12-72 months). Intraocular pressure (IOP) was reduced from a mean preoperative IOP of 36.5 +/- 10.7 mmHg (range, 21-80 mmHg) to 15.3 +/- 6.0 mmHg (range, 1-34 mmHg), and the number of glaucoma medications decreased from 2.6 +/- 0.6 (range, 1-5) before the time of surgery to 0.5 +/- 0.9 (range, 0-4) medications at last follow-up. Overall, there were 67 eyes (54%) that were classified as complete successes, 27 eyes (22%) that were qualified successes, and 30 eyes that failed (24%). Postoperative complications occurred in 43 eyes (34.7%), and 21 eyes (17%) required further surgical intervention and revision. There was no statistically significant difference between the 250-mm(2) and 350-mm(2) type of implants in terms of success rates, final IOP, number of medications, and rates of complications. After adjusting for gender, preoperative IOP, and length of follow-up, increasing age (odds ratio [OR], 1.05; 95% confidence interval [CI], 1.01-1.09; P = 0.02) and the number of previous operations performed before implant surgery (OR, 1.57; 95% CI, 1.07-2.31; P = 0.01) were found to be correlated positively with failure.

CONCLUSIONS:
In Asian eyes with complicated glaucoma, Baerveldt glaucoma implants achieve stable and satisfactory IOP reduction with low incidence of complications in the intermediate term after surgery.

Refractive errors, axial ocular dimensions, and age-related cataracts: the Tanjong Pagar survey.
Wong TY1, Foster PJ, Johnson GJ, Seah SK.

Abstract
PURPOSE:
To describe the relationship of refractive errors and axial ocular dimensions and age-related cataract.

METHODS:
Population-based, cross-sectional survey of ocular diseases among Chinese men and women aged 40 to 81 years (n = 1232) living in the Tanjong Pagar district in Singapore. As part of the examination, refraction and corneal curvature were determined with an autorefractor, with refraction further refined subjectively. Ocular dimensions, including axial length, anterior chamber depth, lens thickness, and vitreous chamber depth, were measured with an A-mode ultrasound device. Lens opacity was graded clinically according to the Lens Opacity Classification System (LOCS) III system. Refraction, biometry, and cataract data on right (n = 989) and left (n = 995) eyes were analyzed separately.

RESULTS:
In analyses controlling for age, gender, education, diabetes, and cigarette smoking, nuclear cataract was associated with myopia (-1.35 D vs. -0.11 D, P < 0.001, comparing right eyes with and without nuclear cataract), but not with any specific biometric component. Cortical cataract was associated with thinner lenses (4.67 mm vs. 4.79 mm, P = 0.001, comparing right eyes with and without cortical cataract), but not with refraction and other biometric components. Posterior subcapsular cataract was associated with myopia (-1.80 D vs. -0.39 D, P < 0.001, comparing right eyes with and without posterior subcapsular cataract), deeper anterior chamber (3.00 mm vs. 2.89 mm, P = 0.02), thinner lens (4.62 mm vs. 4.77 mm, P = 0.001), and longer vitreous chamber (15.78 mm vs. 15.57 mm, P = 0.09), but not with overall axial length and corneal curvature. Adjustment for vitreous chamber depth attenuated the association between posterior subcapsular cataract and myopia by 65.5%, but did not substantially change the association between nuclear cataract and myopia.

CONCLUSIONS:
These population-based data support the associations between nuclear and posterior subcapsular cataracts and myopia reported in previous studies. Posterior subcapsular cataract is also associated with deeper anterior chamber, thinner lens, and longer vitreous chamber, with vitreous chamber depth explaining most of the association between posterior subcapsular cataract and myopia.

A prospective ultrasound biomicroscopy evaluation of changes in anterior segment morphology after laser iridotomy in Asian eyes.
Gazzard G1, Friedman DS, Devereux JG, Chew P, Seah SK.

Abstract
PURPOSE:
To prospectively quantify changes in anterior segment morphology after laser iridotomy using gonioscopy and ultrasound biomicroscopy (UBM).

DESIGN:
Prospective comparative observational case series.

PARTICIPANTS:
Fifty-five fellow eyes of patients presenting with acute primary angle closure (APAC).

METHODS:
The fellow eyes of patients presenting with APAC were examined with UBM, A-scan ultrasonography, and optical pachymetry at presentation and 2 weeks after sequential argon/neodymium yttrium-aluminum-garnet laser peripheral iridotomy (LPI). UBM images were analyzed using UBM Pro 2000 software. Baseline measurements were made both under standard lighting conditions and in darkness to look for changes in anterior segment findings.

MAIN OUTCOME MEASURES:
The degree of angle opening was measured using the angle-opening distance (AOD) at 250 and 500 microm from the scleral spur (AOD250 and AOD500, respectively) and angle recess area (ARA).

RESULTS:
Fifty-five Asian patients were examined; AOD250, AOD500, and ARA all significantly increased after sequential laser iridotomy (P < 0.002). Gonioscopic grading of the angle opening significantly increased in all 4 quadrants (P < 0.001). The Van Herick grade of limbal anterior chamber depth increased (P < 0.001), whereas the number of eyes classified as occludable decreased (73%-33%, P < 0.001). Anterior chamber depth did not change significantly (2.41 mm +/- 0.28 mm vs. 2.42 mm +/- 0.30 mm, P = 0.43) as measured with optical pachymetry. Increased illumination increased the angle-opening measures, but induced a different alteration in peripheral iris morphology. Illumination-induced changes were greater after iridotomy than before laser treatment.

CONCLUSIONS:
In Asian eyes at high risk of developing APAC, sequential LPI produced a significant widening of the anterior chamber angle without deepening the anterior chamber centrally. LPI produces changes in iris morphology that are different from those caused by an increase in illumination, indicating that different mechanisms account for angle opening under these 2 conditions.

The severity and spatial distribution of visual field defects in primary glaucoma: a comparison of primary open-angle glaucoma and primary angle-closure glaucoma.
Gazzard G1, Foster PJ, Viswanathan AC, Devereux JG, Oen FT, Chew PT, Khaw PT, Seah SK.

Abstract
OBJECTIVE:
To compare the characteristics of visual field defects in primary angle-closure glaucoma (PACG) and primary open-angle glaucoma (POAG).

METHODS:
Subjects with primary glaucoma aged 30 years and older were prospectively considered for inclusion. Automated static white-on-white perimetry was performed. A minimum of 2 reliable tests was required with a mean deviation (MD) within 2 dB on 2 tests. Subjects with previous symptomatic angle-closure, normal-tension glaucoma, visually significant cataract, or previous intraocular surgery were excluded.

RESULTS:
Of 234 subjects assessed, 129 had POAG, and 105 had PACG. The MDs (POAG group, -13.3 dB; PACG group, -18.0 dB) indicated more severe visual loss in subjects with PACG. In subjects with POAG, the superior hemifield was more severely affected than the inferior. This was less pronounced in subjects with PACG. Following stratification by MD, the difference between hemifields was marked in the mild (-10 dB<or=MD) and moderate (-20 dB<or=MD<-10 dB) subgroups but was not present in the severe (MD<-20 dB) subgroup. We detected differences between POAG and PACG in retinal sensitivity between the superior and inferior hemifields, independent of severity of damage.

CONCLUSIONS:
The pattern of visual field loss was different in the 2 diseases. This may give insight into the pattern of visual loss in predominantly pressure-dependent glaucomatous optic neuropathy.

Prevalence of lens opacity in Chinese residents of Singapore: the tanjong pagar survey.
Seah SK1, Wong TY, Foster PJ, Ng TP, Johnson GJ.

Abstract
OBJECTIVE:
To determine the prevalence of lens opacity among Chinese residents of Singapore.

DESIGN:
Population-based, cross-sectional survey.

PARTICIPANTS:
Chinese men and women aged 40 years or more in Singapore.

METHODS:
A stratified, clustered, random sampling method, with more weights given to the older age groups, was used to initially select 2000 Chinese persons aged 40 to 79 years from the 1996 electoral register in the Tanjong Pagar district in Singapore. Eligible subjects (n = 1717) were invited for a comprehensive ocular examination at a centralized clinic, after which nonrespondents were examined in their homes with portable instruments.

MAIN OUTCOME MEASURES:
Lens opacity, as determined clinically at the slit lamp using a modification of the Lens Opacity Classification System III. Prevalence rates were age adjusted to the 1997 Singapore census population.

RESULTS:
Of the 1232 persons examined (71.8%), 1206 (70.2%) provided lens data for this analysis. The age-adjusted prevalence of any cataract surgery was 5.1% (95% confidence interval [CI], 3.6, 6.5), with similar rates between men and women. The age-adjusted prevalence of specific types of lens opacity was 22.6% (95% CI, 19.8, 25.4) for any nuclear opacity, 23.9% (95% CI, 21.0, 26.8) for any cortical opacity, and 7.0% (95% CI, 5.3, 8.8) for any posterior subcapsular opacity. The overall age-adjusted prevalence of any cataract or cataract surgery was 34.7% (95% CI, 31.5, 38.0), increasing from 7.0% in those 40 to 49 years and to 94.3% in those 70 years and older (P < 0.001, test for trend for age). When the prevalence of distinct types of lens opacity in an eye was considered, the most common was mixed (age-adjusted prevalence, 11.5%, based on right eye data), followed by nuclear only (9.7%), cortical only (8.3%), and posterior subcapsular only (0.6%). For all cataract types, the prevalence was similar in men and women and was higher in persons examined at their homes than in those examined at the study clinic.

CONCLUSIONS:
These population-based data suggest that cataract is common among adult Chinese residents in Singapore, despite ready access to cataract surgical services. Persons accepting the offer of free eye examinations were less likely to have cataract than those who did not take up this offer.

Angular regression and the detection of the seasonal onset of disease.
Gao F1, Seah SK, Foster PJ, Chia KS, Machin D.

BACKGROUND:
In examining the seasonality of onset of a disease over the year, investigators attempt to identify the peak of onset, and its magnitude. A second objective is to see if the day in which the disease manifests itself is related to subject-specific characteristics or environmental factors.

METHOD:
This paper describes appropriate statistical methodology for the situation where seasonality can be summarised by either a single peak or several peaks, possibly determined by patient characteristics or external influences. The circular, rather than linear, nature of the day of onset of a disease (irrespective of year) requires angular regression techniques to assess these relations, and the von Mises distribution replaces the normal distribution in this context.

RESULTS:
The methods outlined are illustrated by a national study of those experiencing an attack of acute primary angle-closure glaucoma in Singapore.

CONCLUSIONS:
We recommend re-analyses of already published work on seasonality of disease using this angular methodology. We anticipate that this may provide both useful further insight into aspects of aetiology and case studies for the methods themselves.

Education, socioeconomic status, and ocular dimensions in Chinese adults: the Tanjong Pagar Survey.
Wong TY1, Foster PJ, Johnson GJ, Seah SK.

Abstract
AIM:
To relate indices of education, occupation, and socioeconomic status to ocular dimensions and refraction in an adult population.

METHODS:
A population based, cross sectional survey of adult Chinese aged 40-81 years residing in the Tanjong Pagar district in Singapore. Ocular dimensions, including axial length, anterior chamber depth, lens thickness, and vitreous chamber depth, were measured using an A-mode ultrasound device. Corneal radius of curvature and refraction were determined with an autorefractor, with refraction further refined subjectively, and lens nuclear opacity was graded clinically using the modified Lens Opacity Classification System III score. Data on education, occupation, income, and housing type were obtained from a standardised interview.

RESULTS:
Biometric data were available on 951 phakic subjects. After controlling for age, sex, occupation, income and housing type, higher education was associated with longer axial lengths (0.60 mm; 95% confidence interval (CI): 0.34, 0.85, for every 10 years of education), longer vitreous chambers (0.53 mm; 95% CI: 0.30, 0.77), and more myopic refractions (-1.50 dioptres, 95% CI: -2.08, -0.92). Adjustment for axial length attenuated the refractive association of education (-0.68 dioptre, 95% CI: -1.14, -0.21). Similarly, near work related occupations (managers, professionals, and office workers) and higher income were independently associated with longer axial lengths, longer vitreous chambers, and more myopic refractions, and adjustment for axial length attenuated the refractive associations.

CONCLUSIONS:
Adults with greater education, near work related occupations, and higher income are more likely to have longer axial lengths and vitreous chambers, and more myopic refractions. The refractive associations of education, occupation, and income are largely explained by variations in axial length.

Additive effect of unoprostone and latanoprost in patients with elevated intraocular pressure.
Aung T1, Chew PT, Oen FT, Chan YH, Thean LH, Yip L, Lim BA, Soh J, Seah SK.

Abstract
AIMS:
To assess the additive effect of unoprostone and latanoprost in patients with primary open angle glaucoma (POAG) or ocular hypertension (OHT) METHODS: 32 patients with POAG or OHT were randomised to receive either latanoprost once daily or unoprostone twice daily for 4 weeks. After 4 weeks, all patients received both latanoprost and unoprostone for another 4 weeks. The IOP was measured at 9 am and 5 pm on the baseline, day 28, and day 56 visits, and at 9 am on day 14 and day 42 visits. The medications were given to the patients in an open label fashion. The observer was masked to the treatment given. The mean of the measurements was calculated. Safety parameters were also recorded. The additive effect of the medications was assessed by the reduction in intraocular pressure (IOP) when both medications were used, compared with when one medication was used.

RESULTS:
28 patients completed both treatment periods and had IOP data available for evaluation. After 1 month of treatment, latanoprost significantly reduced IOP (mean by 6.1 (SEM 0.8) mm Hg (p<0.001) and unoprostone by 4.9 (1.0) mm Hg (p<0.001) from the baseline of 24.4 (0.6) mm Hg and 24.4 (1.1) mm Hg respectively (p = 0.18). When latanoprost once daily was given to patients treated with unoprostone, there was additional IOP lowering of 1.9 (0.6) mm Hg (p = 0.012). However, adding unoprostone to those being treated with latanoprost produced an IOP change of +0.4 (0.5) mm Hg (p = 0.42). Ocular symptoms and findings were mild and equally distributed between treatment groups, and after combined therapy. Hyperaemia and ocular irritation were the most frequently reported events. Over a third of patients experienced ocular irritation with the combination of medications.

CONCLUSIONS:
Latanoprost once daily causes additional IOP lowering in eyes which were being treated with unoprostone twice a day. However, there was no additional IOP lowering when unoprostone was added to eyes which were being treated with latanoprost. Both drugs were well tolerated together with few ocular adverse events.

Biometric gonioscopy and the effects of age, race, and sex on the anterior chamber angle.
Congdon NG1, Foster PJ, Wamsley S, Gutmark J, Nolan W, Seah SK, Johnson GJ, Broman AT.

Abstract
AIM:
To utilise a novel method for making measurements in the anterior chamber in order to compare the anterior chamber angles of people of European, African, and east Asian descent aged 40 years and over.

METHODS:
A cross sectional study on 15 people of each sex from each decade from the 40s to the 70s, from each of three racial groups-black, white, and Chinese Singaporeans. Biometric gonioscopy (BG) utilises a slit lamp mounted reticule to make measurements from the apparent iris insertion to Schwalbe's line through a Goldmann one mirror goniolens. The main outcome measures were BG measurements of the anterior chamber angle as detailed above.

RESULTS:
There was no significant difference in angle measurement between black, white, and Chinese races in this study. However, at younger ages people of Chinese race appeared to have deeper angles than white or black people, whereas the angles of older Chinese were significantly narrower (p = 0.004 for the difference in slope of BG by age between Chinese and both black and white people).

CONCLUSION:
The failure to detect a difference in angle measurements between these groups was surprising, given the much higher prevalence of angle closure among Chinese. It appears that the overall apparent similarity of BG means between Chinese and Western populations may mask very different trends with age. The apparently more rapid decline in angle width measurements with age among Chinese may be due to the higher prevalence of cataract or "creeping angle closure." However, longitudinal inferences from cross sectional data are problematic, and this may represent a cohort phenomenon caused by the increasing prevalence of myopia in the younger Singaporean population.

The relationship between ocular dimensions and refraction with adult stature: the Tanjong Pagar Survey.
Wong TY1, Foster PJ, Johnson GJ, Klein BE, Seah SK.

Abstract
PURPOSE:
To describe the association of ocular dimensions and refraction with adult stature.

METHODS:
This was a population-based cross-sectional survey of adult Chinese aged 40 to 81 years residing in the Tanjong Pagar district in SINGAPORE: As part of the examination, ocular dimensions, including axial length, anterior chamber depth, lens thickness, and vitreous chamber depth, were measured using an A-mode ultrasound device. Corneal radius and refraction were determined with an autorefractor, with refraction further refined subjectively. Height (in meters) and weight (in kilograms) were measured using a standardized protocol, and body mass index (BMI) was calculated as weight divided by the square of the height (kilograms per square meter).

RESULTS:
Data on ocular biometry, refraction, height, and weight were available on 951 (55.4%) participants with phakic eyes. After controlling for age, sex, education, occupation, housing type, income, and weight, it was found that taller persons were more likely to have longer axial lengths (+0.23 mm longer axial length, for every 0.10 m difference in height), deeper anterior chambers (+0.07 mm), thinner lenses (-0.09 mm), longer vitreous chambers (+0.26 mm), and flatter corneas (+0.09 mm longer corneal radius), although refractions were similar. In contrast, heavier persons tended to have more hyperopic refractions (+0.22 D for every 10 kg difference in weight, +0.56 D for every 10 kg/m(2) difference in BMI) but similar ocular dimensions.

CONCLUSIONS:
Adult height is independently related to ocular dimensions, but does not appear to influence refraction. Thus, although taller persons are more likely to have longer globes, they also tend to have deeper anterior chambers, thinner lenses, and flatter corneas. Conversely, weight is independently related to refraction, although the exact biometric component responsible for this association is not apparent.

The prevalence and risk factors for pterygium in an adult Chinese population in Singapore: the Tanjong Pagar survey.
Wong TY1, Foster PJ, Johnson GJ, Seah SK, Tan DT.

Abstract
PURPOSE:
To determine the prevalence and risk factors for pterygium in the Chinese population of Singapore.

METHODS:
A population-based survey was conducted in Singapore, an island located 1 degree north of the equator with a stable tropical climate. A disproportionate, stratified, clustered, random sampling procedure was used to select the names of 2000 Chinese people aged 40 to 79 years from the 1996 electoral register in the Tanjong Pagar district of Singapore. Selected subjects underwent a comprehensive interview and ocular examination. Pterygium was diagnosed and graded clinically as grade 1 (transparent), 2 (intermediate), and 3 (opaque). Risks factors associated with pterygium and grade 3 pterygium were evaluated with logistic regression models.

RESULTS:
From a total of 1717 eligible subjects, 1232 (71.8%) were examined. There were 120 people with either unilateral (n = 70) or bilateral (n = 50) pterygium, equivalent to an overall prevalence of 6.9% (95% confidence interval [CI], 5.2, 8.8) in the Chinese population aged 40 and older. The prevalence increased linearly with age (chi-square test of trend P <.001) and was higher among men than women (age-adjusted odds ratio [OR], 4.2; 95% CI, 2.5, 6.9). Men aged 70 and above had the highest overall prevalence of 25.4% (95% CI, 18.2, 19.4), but pterygium was not seen in women aged 40 to -49 years. In multivariate analysis, ptergyium was independently associated with increasing age (OR, 7.8; 95% CI, 3.2, 18.8 for persons 70 to 81 years, compared with 40 to 49 years), male sex (OR, 5.1; 95% CI, 2.9, 9.3) and certain occupations; factory workers, production workers and machine operators (OR, 3.1; 95% CI, 1.5, 6.3), as well as laborers and agricultural workers (OR, 3.3; 95% CI, 1.6, 7.0) had higher risks, compared with professionals and office workers. Grade 3 pterygium (n = 36) was also independently associated with male sex (OR, 11.6; 95% CI, 3.5, 38.6) and similar occupations but was not related to age.

CONCLUSIONS:
The prevalence of pterygium in Singapore is 7% among Chinese aged 40 years and older. Independent associations with increasing age, male sex, and occupations linked to outdoor work and other exposures suggest a multifactorial cause of this condition.

Automated static perimetry: the influence of myopia and its method of correction.
Aung T1, Foster PJ, Seah SK, Chan SP, Lim WK, Wu HM, Lim AT, Lee LL, Chew SJ.

Abstract
OBJECTIVE:
To determine how the magnitude of myopia and its method of correction influence visual field testing.

DESIGN:
Prospective observational case series, including comparison of spectacles and contact lenses.

PARTICIPANTS:
One hundred forty-six ophthalmologically normal males 19 to 24 years of age with myopia (spherical equivalent from -0.50 to -14.0 diopters).

METHODS:
Participants performed automated static threshold perimetry. Refractive errors were corrected using trial lenses and soft contact lenses. Subjects were tested with both methods of correction, the order of which was randomized.

MAIN OUTCOME MEASURES:
Threshold sensitivity and global indexes.

RESULTS:
Only one subject (0.7%) had a significant reproducible visual field defect on both methods of correction. Six subjects (4.1%) had a focal visual field defect on one method of correction but not the other. For myopia greater than -4.0 diopters, the mean defect decreased significantly as axial length and degree of myopia increased (P: < 0.01). Similar results were obtained with either method of correction.

CONCLUSIONS:
Threshold sensitivity is reduced in moderate and high myopia, regardless of the method of correction. The surprisingly low prevalence of visual field defects in this myopic population disputes the widely held view that myopia is associated commonly with visual field abnormalities. If field defects are found in myopes on automated perimetry, it is advisable to repeat the test with another method of optical correction to check that such defects are genuine and not related to the method of refractive correction.

Variations in ocular biometry in an adult Chinese population in Singapore: the Tanjong Pagar Survey.
Wong TY1, Foster PJ, Ng TP, Tielsch JM, Johnson GJ, Seah SK.

Abstract
PURPOSE:
To describe the variation in ocular biometry in adult Chinese individuals in Singapore.

METHODS:
This study was a population-based, cross-sectional survey of adult Chinese persons aged 40 to 81 years residing in Tanjong Pagar district, Singapore. Axial ocular dimensions, including axial length (AL), anterior chamber depth (ACD), lens thickness (LT), and vitreous chamber depth (VCD) were measured using an A-scan ultrasound device. Corneal curvature (CC) and noncycloplegic refraction were measured with an autorefractor, with refraction further refined subjectively. Lens nuclear opacity (NO) was graded clinically using the modified Lens Opacity Classification System III (LOCS III) score.

RESULTS:
A total of 1717 subjects were eligible for the survey, of whom 1232 (71.8%) participated. Biometric and refraction data were available for 1004 (58.5%) phakic subjects. The AL, ACD, LT, VCD, CC, and LOCS III scores were 23.23 +/- 1.17 mm, 2.90 +/- 0.44 mm, 4.75 +/- 0.47 mm, 15.58 +/- 1.11 mm, 7.65 +/- 0.27 mm, and 3.2 +/- 0.9 (mean +/- SD), respectively. On average, people aged 40 to 49 years, when compared with those 70 to 81 years, had longer ALs (mean difference, +0.58 mm), deeper ACDs (+0.52 mm), longer VCDs (+0.72 mm), but thinner lenses (-0.70 mm) and less severe NO (-1.7 LOCS III score). CCs did not vary significantly with age. After controlling for age, women had shorter ALs and VCDs, shallower ACDs, but thicker lenses and steeper CCs than men. The variation in noncycloplegic refraction with age was nonlinear. Among people aged 40 to 59 years, a higher prevalence of hyperopia was seen in older compared with younger persons (on average, a difference of +1.3 D for every 10-year difference in age, P: < 0.001), explained principally by shorter AL (and VCD) in older persons. Among those 60 to 81 years, this pattern was not obvious (a difference of -0.03 D for every 10-year difference in age, P: = 0.12), as NO became an additional determinant of refraction, with greater degrees of NO in older person's driving refraction in the "minus" direction.

CONCLUSIONS:
Ocular dimensions vary with age and gender in adult Chinese persons in Singapore. The variation in noncycloplegic refraction in people 40 years and older may be explained by differences in axial lengths (principally vitreous chamber depths) between older and younger persons and, from 60 years onwards, differences in lens nuclear opacification as well.

Rates of hospital admissions for primary angle closure glaucoma among Chinese, Malays, and Indians in Singapore.
Wong TY1, Foster PJ, Seah SK, Chew PT.

Abstract
AIM:
To estimate the rates of hospital admissions for primary angle closure glaucoma (PACG) in Chinese, Malays, and Indians in Singapore

METHODS:
A population-wide hospital discharge database in Singapore was used to identify all hospital admissions with a primary discharge diagnosis of PACG (International Classification of Disease-CM code: 365.2). The Singapore census was used for denominator data.

RESULTS:
Between 1993 and 1997 there were 894 hospital admissions for PACG. The mean annual rate of PACG admissions was 11.1 per 100 000 (95% confidence interval (CI), 10.4, 11.8) among people aged 30 years and over. The annual rate was highest for Chinese (age and sex adjusted rate: 12.2 per 100 000), which was twice that of Malays (6.0 per 100 000) and Indians (6.3 per 100 000). Females had two times higher rates than males in all three races (age adjusted relative risk: 2.0, 95% CI: 1.7, 2.3).

CONCLUSION:
Malay and Indian people had identical rates of hospital admissions for PACG, which were only half the rates compared with Chinese.

Prevalence and risk factors for refractive errors in adult Chinese in Singapore.
Wong TY1, Foster PJ, Hee J, Ng TP, Tielsch JM, Chew SJ, Johnson GJ, Seah SK.

Abstract
PURPOSE:
To determine the epidemiology of refractive errors in an adult Chinese population in Singapore.

METHODS:
A disproportionate, stratified, clustered, random-sampling procedure was used to select names of 2000 Chinese people aged 40 to 79 years from the 1996 Singapore electoral register in the Tanjong Pagar district in Singapore. These people were invited to a centralized clinic for a comprehensive eye examination, including refraction. Refraction was also performed on nonrespondents in their homes. Myopia, high myopia, and hyperopia were defined as a spherical equivalent (SE) in the right eye of less than -0.5 D, less than -5.0 D, and more than +0.5 D, respectively. Astigmatism was defined as less than -0.5 D of cylinder. Anisometropia was defined as a difference in SE of more than 1.0 D between the two eyes. Only phakic eyes were analyzed.

RESULTS:
From 1717 eligible people, 1232 (71.8%) were examined. Adjusted to the 1997 Singapore population, the overall prevalence of myopia, hyperopia, astigmatism, and anisometropia was 38.7% (95% confidence interval [CI]: 35.5, 42.1), 28.4% (95% CI: 25.3, 31.3), 37.8% (95% CI: 34.6, 41.1), and 15.9% (95% CI: 13.5, 18.4), respectively. The prevalence of high myopia was 9.1% (95% CI: 7.2, 11.2), with women having significantly higher rates than men. The age pattern of myopia was bimodal, with higher prevalence in the 40 to 49 and 70 to 81 age groups and lower prevalence between those age ranges. Prevalence was reversed in hyperopia, with a higher prevalence in subjects aged 50 to 69. There was a monotonic increase in prevalence with age for both astigmatism and anisometropia. Increasing educational levels, higher individual income, professional or office-related occupations, better housing, and greater severity of nuclear opacity were all significantly associated with higher rates of myopia, after adjustment for age and sex.

CONCLUSIONS:
The results indicate that whereas myopia is 1.5 to 2.5 times more prevalent in adult Chinese residing in Singapore than in similarly aged European-derived populations in the United States and Australia, the sociodemographic associations are similar.

The prevalence of glaucoma in Chinese residents of Singapore: a cross-sectional population survey of the Tanjong Pagar district.
Foster PJ1, Oen FT, Machin D, Ng TP, Devereux JG, Johnson GJ, Khaw PT, Seah SK.

Abstract
BACKGROUND:
Data on prevalence of glaucoma in East Asia are scarce.

OBJECTIVE:
To determine the prevalence and clinical characteristics of glaucoma in adult Chinese Singaporeans.

METHODS:
A group of 2000 Chinese people, aged 40 to 79 years, were selected from the electoral register of Tanjong Pagar district in Singapore using a disproportionate, stratified, clustered, random-sampling procedure. Glaucoma was diagnosed in people with an excavated optic neuropathy and a reproducible visual field defect or on the basis of severe structural disc abnormality alone, if reliable field results could not be obtained. The diagnosis was also made in blind subjects with raised intraocular pressure or previous glaucoma surgery.

RESULTS:
Of 1717 eligible subjects, 1232 were examined, with a response rate of 71.8%. There were 45 cases of glaucoma: 27 were men and 18 were women. The main diagnoses were primary open-angle glaucoma (n = 22 [49%]), primary angle-closure glaucoma (n = 14 [31%]), and secondary glaucoma (n = 7 [16%]). It was not possible to determine the mechanism in 2 (4%).

CONCLUSIONS:
The age-standardized prevalence of glaucoma was 3.2% (95% confidence interval, 2.3-4.1) in the population 40 years and older. Glaucoma was the leading cause of blindness. Primary angle-closure glaucoma and secondary glaucoma were the most visually destructive forms of the disease. Our findings suggest current projections of glaucoma prevalence among ethnic Chinese are a substantial underestimate.

Trabeculectomy for acute primary angle closure.
Aung T1, Tow SL, Yap EY, Chan SP, Seah SK.

Abstract
OBJECTIVE:
To analyze the results of trabeculectomy performed for all cases of acute primary angle closure (APAC).

DESIGN:
Retrospective, noncomparative case series

PARTICIPANTS:
Fifty-six consecutive patients who underwent trabeculectomy for APAC at two Singapore centers from 1993 through 1995.

METHODS:
The conventional treatment for APAC is to lower intraocular pressure (IOP) medically, after which laser peripheral iridotomy (PI) is performed. However, in Asian eyes, the acute attack is often refractory to standard treatment. Trabeculectomy is occasionally performed on eyes that do not respond to medical therapy, as well as eyes with APAC that respond to medical therapy but are assessed as having underlying chronic angle-closure glaucoma. In such cases, laser PI is not performed before trabeculectomy.

MAIN OUTCOME MEASURES:
The surgical outcome was assessed in terms of final IOP and the incidence of complications. Success was defined as final IOP less than 21 mmHg without medication, and qualified success was defined as final IOP less than 21 mmHg with medication. Patients whose IOP was more than 21 mmHg, required further glaucoma surgery, lost light perception, or whose eye became phthisical were classified as failures.

RESULTS:
The mean follow up was 22 months (range, 6-42 months). In group A, the medical failure group (n = 32), success in IOP control was obtained in 18 patients (56.2%), qualified success was achieved in 3 patients (9.4%), and failure resulted in 11 patients (34.4%). Ten patients (31.3%) encountered early postoperative complications such as shallow anterior chamber. In group B, the medical success group (n = 24), success in IOP control was achieved in 21 patients (87.5%), qualified success was achieved in 3 patients (12.5%), and there were no cases of failure. The incidence of postoperative complications was low (4 eyes [16.7%]). In terms of IOP outcome, trabeculectomy outcome was significantly worse in group A (P<0.001, Fisher's exact test).

CONCLUSIONS:
Because there is a high risk of surgical failure and complications, trabeculectomy may not be the procedure of choice in medically unresponsive cases of APAC.

Augmentation of filtering blebs with perfluoropropane gas bubble: an experimental and pilot clinical study.
Wong HT1, Seah SK.
Erratum in
Ophthalmology 1999 Aug;106(8):1458. Tym WH [corrected to Wong HT].

Abstract
OBJECTIVE:
To evaluate the use of perfluoropropane (C3F8) gas bubble in the augmentation of glaucoma-filtering blebs.

DESIGN:
Experimental animal study and a pilot clinical study.

PARTICIPANTS:
Twenty rabbits in the animal study and 20 humans in the pilot study participated.

INTERVENTION:
Twenty patients underwent trabeculectomy for medically uncontrolled glaucoma. Surgical techniques were similar to those used in standard limbus-based trabeculectomies. The Tenon's capsule and conjunctival wound were closed separately using continuous sutures. Before the final knots were tied, 0.1 to 0.2 ml of 15%:85%-C3F8:air mixture gas bubble was introduced into the subconjunctival space with a silicone tube attached to a 27-gauge Rycrof cannula. The sutures were immediately knotted on withdrawal of the tube. The patients were reviewed after surgery for the appearance, size, and location of the gas bubble. The bleb morphology and intraocular pressures were also monitored.

MAIN OUTCOME MEASURES:
The parameters measured were intraocular pressure control, Snellen visual acuity, appearance of the bleb in relation to its elevation and degree of inflammation of the subconjunctival tissue, and characteristics of the gas bubble (e.g., size, number, and position).

RESULTS:
The gas bubbles stayed in the conjunctival bleb for an average duration of 17 days (range, 13-27 days). In all cases, the gas bubbles helped to maintain the filtering bleb until their complete resolution. No excessive inflammation was noted in the filtering blebs. The mean preoperative intraocular pressure was 27.3 +/- 5.5 millimeters of mercury (mmHg), and the mean postoperative intraocular pressure was 14.5 +/- 2.3 mmHg, with only two patients requiring supplementary topical medication. All cases resulted in good filtering blebs with satisfactory intraocular pressures after 16 months of follow-up.

CONCLUSIONS:
Subconjunctival C3F8 gas bubbles, via a "spacer" effect, aid the maintenance of filtering blebs in the early postoperative period. This technique may be useful in augmenting or salvaging blebs at risk of failure.

Glaucoma drainage implants in Asian eyes.
Aung T1, Seah SK.

Abstract
OBJECTIVE:
Previous studies have suggested that there are racial differences in the outcome of conventional filtration surgery. This study aims to evaluate the outcome of glaucoma drainage implants in Asian eyes with complicated glaucoma and to determine whether there are racial differences in the results of such implant surgery compared to previous reports in non-Asian patients.

DESIGN:
The study design was a retrospective review of all patients with more than 6-months' follow-up after glaucoma implant surgery at the Singapore National Eye Centre between January 1993 and August 1996.

PARTICIPANTS:
A total of 83 Asian patients with uncontrolled complicated glaucoma participated.

INTERVENTION:
A total of 29 patients received Molteno implants and 54 received Baerveldt implants.

MAIN OUTCOME MEASURES:
The surgical outcome was assessed in terms of final intraocular pressure (IOP), visual acuity outcome, and incidence of complications. Success was defined as final IOP less than 22 mmHg with no medications and qualified success as an IOP less than 22 mmHg with medication.

RESULTS:
With mean follow-up of 13.41 months, success in IOP control was achieved in 73.5% of patients and qualified success in 12%. Visual acuity remained stable or improved in 85.5%. There were no patients who encountered intraoperative complications, and the incidence of serious postoperative complications was low. The most frequently observed short- and long-term postoperative complication was hyphema in 14 eyes (16.9%) and bullous keratopathy in 7 eyes (8.4%), respectively.

CONCLUSIONS:
Glaucoma drainage implants have good outcome and visual stabilization in Asian eyes with success rates for IOP control comparable to those reported in previous studies in non-Asian eyes.

Incidence of acute primary angle-closure glaucoma in Singapore. An island-wide survey.
Seah SK1, Foster PJ, Chew PT, Jap A, Oen F, Fam HB, Lim AS.

Abstract
OBJECTIVES:
To determine the incidence of acute primary angle-closure glaucoma (APACG) in Singapore and to identify demographic and meteorological risk factors.

DESIGN:
A prospective, island-wide incidence study.

SETTING:
All government and private ophthalmological practices in Singapore, from March 1, 1995, to February 29, 1996.

METHODS:
New cases of APACG were identified by all ophthalmologists in Singapore during a 1-year period. Demographic and clinical details were recorded.

RESULTS:
One hundred eighty-nine people (208 eyes) were seen with APACG for the first time during the 1-year period. These new cases represent an incidence of 12.2 per 100,000 per year (95% confidence interval, 10.5-13.9) in those aged 30 years and older. Major risk factors identified were female sex (relative risk, 2.4), Chinese ethnic origin (relative risk, 2.8), and age of 60 years or older (relative risk, 9.1). Half of those affected were seen 3 days or more after the onset of symptoms. Attacks were more frequent on hotter days. There also was a relationship between the number of attacks per day and the mean number of sunspots and mean solar radio flux during the previous 30 days.

CONCLUSIONS:
There is a high incidence of APACG in Singapore, with elderly women being the highest risk group. Chinese Singaporeans are at higher risk than other ethnic groups (Malay and Indian). There is often a substantial delay before these patients consult a physician. The onset of APACG seems to be associated with meteorological factors.

Cataract surgery after trabeculectomy.
Seah SK1, Jap A, Prata JA Jr, Baerveldt G, Lee PP, Heuer DK, Minckler DS.

Abstract
BACKGROUND AND OBJECTIVE:
To determine the effect of cataract surgery on glaucomatous eyes with good intraocular pressure (IOP) control after trabeculectomy.

PATIENTS AND METHODS:
Twenty-two eyes with functional blebs that underwent cataract extraction were retrospectively analyzed.

RESULTS:
The mean (+/- SD) preoperative IOP was 11.0 +/- 4.3 mm Hg. The mean (+/- SD) postoperative IOPs at 1, 2, 6, and 9 months were 15.5 +/- 4.9, 12.6 +/- 4.7, 14.6 +/- 5.6, and 19.0 +/- 7.9 mm Hg, respectively. At each interval except for the second month, the mean IOP was statistically significantly higher than the preoperative value (P = .0003, .24, .02, and .0009, respectively). The total number of medications was also higher (3 preoperatively versus 27 postoperatively). The interval between the two surgeries had no influence on IOP control. Intraoperative complications during cataract surgery, particularly vitreous loss, were associated with poor IOP control. Phacoemulsification had less of an effect on the postoperative IOP control than did extracapsular cataract extraction.

CONCLUSIONS:
Eyes with previous successful trabeculectomies had higher IOPs and required more medications after subsequent cataract surgeries.

Comparison of argon laser iridotomy and sequential argon laser and Nd:YAG laser iridotomy in dark irides.
Lim L1, Seah SK, Lim AS.

Abstract
BACKGROUND AND OBJECTIVE:
A prospective study was performed to compare argon laser iridotomy and sequential argon laser and Nd:YAG laser iridotomy in dark irides.

PATIENTS AND METHODS:
Twenty-four eyes of 17 patients underwent laser iridotomies; 13 underwent argon laser iridotomies and 11 underwent sequential argon laser and Nd:YAG laser iridotomies. The argon laser settings were standardized at 1.2 W, 50-mum spot size, and 0.1-second duration. The Nd:YAG laser was set at 2.5 mJ and single-pulse shots were used.

RESULTS:
All of the iridotomies were patent at the end of one treatment session. The mean total energy used for argon laser iridotomy was 8.28 J. For sequential iridotomy, 3.12 J was used for the argon laser stage and 7.5 mJ for the Nd:YAG laser stage.

CONCLUSION:
The total argon laser energy used can be reduced by 2.65 times by using the sequential laser iridotomy technique.

Visual recovery after trabeculectomy.
Seah SK1, Prata JA Jr, Minckler DS, Lee MB, Baerveldt G, Lee PP, Heuer DK.

Abstract
PURPOSE:
We retrospectively analyzed 155 eyes of 155 patients who underwent trabeculectomy with and without antimetabolites to determine the time for recovery of visual acuity postoperatively and to determine factors associated with delayed recovery of visual acuity and visual loss.

METHODS:
Factors examined included age, race, preoperative visual field grading. Humphrey Field Analyzer's indices (mean deviation and corrected pattern standard deviation), optic nerve cup-to-disk ratio, antimetabolite use, postoperative complications, and postoperative hypotony. The mean age of the patient was 63.6 +/- 15.7 years. Mean follow-up was 14.4 +/- 8.5 months (range 6-30).

RESULTS:
One hundred forty-four patients (93%) regained their preoperative visual acuity, and 11 patients (7%) sustained visual loss. For the 144 patients who regained visual acuity, recovery time ranged between 1 and 244 days (median 6); recovery occurred before the second month in 128 patients (89%) and was delayed beyond 2 months in 16 patients (11%). Among the 60 primary open-angle glaucoma patients with preoperative visual acuity better than 20/200, those with delayed visual recovery had significantly worse preoperative visual field grades than did those with early recovery (p = 0.04). The preoperative Humphrey mean deviation was also higher (16.3 dB vs. 11.2 dB, p = 0.04). All 16 patients with delayed visual recovery also had postoperative hypotony (p = 0.01); this was transient (<2 weeks) in 12 patients and prolonged in four. In patients who failed to regain visual acuity, the visual loss did not correlate with any preoperative risk factors or hypotony, but these patients did have a higher incidence of postoperative complications (p = 0.05).

CONCLUSION:
We conclude that patients with primary open-angle glaucoma who have advanced visual field defects are at greater risk of delayed visual recovery after trabeculectomy and that postoperative hypotony contributes to this delay.

Hypotony following trabeculectomy.
Seah SK1, Prata JA Jr, Minckler DS, Baerveldt G, Lee PP, Heuer DK.

Abstract
OBJECTIVE:
To determine the risk factors for development of postoperative hypotony and the effects of hypotony on the outcome of surgery in terms of intraocular pressure (IOP) control and final visual acuity in patients who underwent standard trabeculectomy, trabeculectomy with postoperative 5-fluorouracil injections, trabeculectomy with intraoperative mitomycin-C, or trabeculectomy with both antimetabolites.

PATIENTS AND DESIGN:
We retrospectively reviewed the outcome in 155 eyes of 155 patients who underwent standard trabeculectomy (n = 15), trabeculectomy with postoperative 5-fluorouracil injections (n = 81), trabeculectomy with intraoperative mitomycin-C (n = 55), or trabeculectomy with both antimetabolites (n = 4).

RESULTS:
Hypotony developed in 108 (69.6%) eyes (IOP < 6 mm Hg) at some point postoperatively; this was transient (< 14 days) in 75 eyes, and prolonged (> 14 days) in 33 eyes. The positive preoperative factors for the development of prolonged hypotony were young age, myopia, and preoperative use of carbonic anhydrase inhibitor. The mean age of patients in whom prolonged hypotony developed was 57.3 +/- 18.3 years (compare the mean age without prolonged hypotony, 65.3 +/- 14.5 years, p = 0.02). Sixteen of 33 (48%) patients in whom prolonged hypotony developed were myopic (p = 0.02), and 23 of 33 (70%) patients in whom prolonged hypotony developed used preoperative carbonic anhydrase inhibitor (p = 0.07).

CONCLUSIONS:
There was no difference in the incidence of hypotony between patients who received 5-fluorouracil and those who received mitomycin-C. Postoperative hypotony was associated with three types of postoperative complications: shallow anterior chamber, choroidal detachment, and hypotony maculopathy (p = 0.02, 0.000, and 0.05, respectively). Hypotony did not have any effect on the success of surgery in terms of IOP control, but did have an effect on the visual outcome. Fourteen of the 33 patients (42.4%) in whom prolonged hypotony developed had worse visual acuity (p = 0.002); of these cases, four were due to hypotony maculopathy.

Postoperative complications and short-term outcome after 5-Fluorouracil or mitomycin-C trabeculectomy.
Prata JA Jr1, Seah SK, Minckler DS, Baerveldt G, Lee PP, Heuer DK.

Abstract
PURPOSE:
This study was performed to compare the postoperative complications between trabeculectomy with 5-fluorouracil injected after surgery and trabeculectomy with mitomycin-C applied intraoperatively.

METHODS:
Retrospective review was done on 77 eyes that had received 5-fluorouracil injections after trabeculectomy, 45 eyes that received mitomycin-C during trabeculectomy, 4 eyes that received both agents, and 15 eyes that received neither agent between January 1991 and July 1992. 5-fluorouracil-treated eyes received a mean of 5 +/- 2.5 subconjunctival injections of 5 mg each (5 mg/0.1 ml). Mitomycin-C-treated eyes received 3-5 min exposure to 0.5 mg/ml mitomycin-C. Several parameters were compared between groups including hypotony defined as intraocular pressure <6 mm Hg. Success was defined as IOP <21 mm Hg with or without medications. Followup averaged 6-12 months.

RESULTS:
Complications including hypotony, loss of visual acuity, choroidal effusion, shallow anterior chamber, cataract progression, hyphema and procedure failure were equivalent between 5-fluorouracil and mitomycin-C-treated groups.

CONCLUSIONS:
Excluding corneal epithelial toxicity that was more common with 5-fluorouracil, the two agents used had similar success and complications during the short followup period.

Contact transscleral cyclophotocoagulation for end stage glaucoma.
Seah SK1, Jap A, Min G.

Abstract
Contact transscleral cyclophotocoagulation is a form of cyclodestructive procedure, which is effective in the lowering of intraocular pressure in eyes with refractory glaucoma by destroying the aqueous humor-producing ciliary processes. Continuous wave Nd:YAG (Neodymium: Yttrium-Aluminium-Garnet) laser is used in the cyclodestruction, the laser energy being delivered to the target tissues transsclerally via a fibre-optic probe. We used the Lasag microruptor III Nd:YAG laser to treat 16 cases of refractory glaucoma to evaluate the effectiveness of laser in pain relief and intraocular pressure control. The mean preoperative intraocular pressure of 48.3 +/- 9.3 mm Hg decreased to 30.6 +/- 17.4 mm Hg (p = 0.0001) during an average follow-up of 294.2 +/- 94.2 days (range, 181-465 days). Retreatment was required in eight of 16 eyes (50%). Four eyes (27%) had decreased vision from perception of light to no perception of light. None of the 15 patients developed phthisis bulbi or other serious complications. We conclude that transscleral cyclophotocoagulation is an effective modality of therapy for refractory and end stage glaucoma. The lower than recommended total energy we used in the treatment protocol was associated with lower incidence of complications but also lower success rate and higher retreatment rate.

Determination of mitomycin C in human aqueous humor and serum by high-performance liquid chromatography.
Li WY1, Seah SK, Koda RT.

Abstract
Mitomycin C (MMC) is used in the treatment of disseminated adenocarcinoma of the stomach and pancreas and is used in ophthalmology as adjunctive therapy in trabeculectomy. Since only small volumes of aqueous humor are available for analysis, a sensitive method requiring limited sample preparation was developed. An internal standard, 4-aminoacetophenone, was added to aqueous humor specimens, and the solution was directly injected into the high-performance liquid chromatographic (HPLC) column. The use of a short 50-mm C18 reversed-phase column gave adequate resolution of peaks with improved sensitivity. The method was applicable for determination of MMC in serum, although solid-phase extraction for sample clean-up was required prior to injection into the HPLC column, and analytical columns of 150-250 mm were necessary for adequate resolution of peaks. The method has been validated and is linear from 6.25 to 50 ng/ml in aqueous humor and from 10 to 500 ng/ml in serum.

Mitomycin-C concentration in human aqueous humour following trabeculectomy.
Seah SK1, Prata JA Jr, Minckler DS, Koda RT, Baerveldt G, Lee PP, Heuer DK.

Abstract
The aim of the study was to determine mitomycin-C (MMC) concentrations in human aqueous humour during trabeculectomy and to correlate anterior chamber concentrations with method of application. MMC was applied intra-operatively by saturating sponges, ranging in size from 2 x 2 x 5 mm to 2 x 4 x 10 mm on dry cut, with 0.5 mg/ml MMC during trabeculectomy for 3-5 minutes. Applications to episclera were made in 18 cases and to the scleral bed after scleral flap dissection in 9 cases. Aqueous samples were collected by paracentesis with a 30 gauge needle 2-7 minutes after removal of sponge and external irrigation. Aqueous MMC concentrations were determined by high-performance liquid chromatography. Aqueous MMC concentration in 27 samples ranged from below minimum detectable concentration (less than 5 ng/ml) to 120.8 ng/ml. Mean aqueous drug levels obtained when the applications were to the scleral bed were 35.65 +/- 39.17 ng/ml (range 5-120.8 ng/ml). Applications on episclera gave mean aqueous concentrations of 4.98 +/- 9.11 ng/ml (range 0-33.3 ng/ml). The difference was statistically significant (p = 0.004). There were no correlations between sponge size, time of MMC exposure and aqueous MMC level. In conclusion, MMC is detectable in aqueous humour within minutes of external application and the aqueous concentration level is higher if the application is in the scleral bed than on the episclera. Toxicity of the drug at this concentration range for corneal endothelial cells needs further investigation via in vitro and clinical studies.

Experimental Trypanosoma cruzi infection in rhesus monkeys 111. Electrocardiographic and histopathological findings.
Miles MA, Marsden PD, Pettitt LE, Draper CC, Watson S, Seah SK, Hutt MS, Fowler JM.

Abstract
In five rhesus monkeys surviving 'Peru strain' or 'strain 7' Trypanosoma cruzi infection for six to eight years, positive xenodiagnosis results and high indirect fluorescent antibody titres (4096 - 65536) persisted until the animals were killed. Abnormal electrocardiograph patterns in two monkeys (H and K) were possibly compatible with myocardial damage. Histopathological changes attributable to T. cruzi infection were minor in four monkeys but severe in one (R). In this animal, infected with what was judged previously to be the less virulent of the two T. cruzi stocks used ('strain 7'), there was severe myocarditis, with myofibre degeneration, and lesions of the oesophagus. Elevated serum levels of five enzymes were not detected in any of the chronically infected monkeys.

Mebendazole in the treatment of helminthiasis.
Seah SK.
Abstract
Mebendazole, a new broad-spectrum anthelmintic, was used to treat patients with nematode infections--ascariasis, trichuriasis and hookworm. The dosage for adults was 100 mg twice daily for 3 days and for children, 50 mg twice daily for 3 days. Pretreatment and post-treatment egg counts on stool specimens showed that after mebendazole there was a reduction of over 99% in egg count per gram of stool in all three types of infection. The overall cure rates for the infections were as follows: Ascaris lumbricoides, 86.8% (59/68); Trichuris trichiura, 86.0% (37/43); and hookworm, 85.7% (24/28). The drug was equally effective in light and heavy infections. No important side effect was noted with this drug. It is suggested that mebendazole is the drug of choice for trichuriasis and mixed nematode infection.

Experimental Trypanosoma cruzi infections in rhesus monkeys. II. The early chronic phase.
Marsden PD, Seah SK, Draper CC, Pettitt LE, Miles MA, Voller A.

Abstract
Information on the acute and early chronic phases of infection with Trypanosoma cruzi in eight rhesus monkeys is reported with particular reference to the pattern of subpatent parasitaemia and serology. Xenodiagnosis was superior to animal inoculation and blood culture in its capacity to detect subpatent parasitaemia. Each monkey showed an individual, relatively constant pattern of this not related to the nature of the inoculum. Levels of indirect fluorescent and indirect haemagglutinating antibodies remained elevated during a year of observations. One monkey died with a megaoesophagus. Another monkey after challenge with a heterologous strain by orbital inoculation failed to develop Romana's sign and showed no change in serum antibody levels or degree of xenopositivity.

The use of irradiated vaccine in immunization against experimental murine toxoplasmosis.
Seah SK, Hucal G.

Abstract
Trophozoites from the peritoneal cavities of mice infected with the RH strain Toxoplasma gondii were given irradiation in doses of 5, 10, 15, and 20 kiloroentgens (kr). CD-1 strain mice that received intraperitoneal inoculation of trophozoites irradiated with 5 kr all died of toxoplasmosis, but the mice that received trophozoites irradiated with the higher doses all survived. The survirors that were examined were found to be free of toxoplasmic cysts. Single doses of these irradiated vaccines provided good protection to subsequent virulent challenge. This protection was 100% in the first 3 weeks after the immunization. Survivors of the first challenge were also solidly protected against a subsequent rechallenge.

Chemotherapy in experimental toxoplasmosis: comparison of the efficacy of trimethoprim-sulfur and pyrimethamine-sulfur combinations.
Seah SK.

Abstract
Mice infected by intraperitoneal inoculation of the RH strain of Toxoplasma gondii were treated with various drugs. Trimethoprim was found to have no effect. Sulphamethoxazole, sulphadiazine and pyrimethamine had significant therapeutic effects on the course of murine toxoplasmosis. The therapeutic efficacy of sulphamethoxazole was enhanced by the addition of trimethoprim. A pyrimethamine-sulphadiazine combination was found to be superior to a trimethoprim-sulphamethoxazole combination in the treatment of experimental murine toxoplasmosis.

Onchocerciasis in Canada.
Seah SK.

Abstract
The first two cases of onchocerciasis seen in Canada are reported. The patients had come from West Africa to study in Canada several months prior to admission to hospital. The presenting symptom in each case was intense pruritus. One of the patients had early ocular involvement. The diagnosis was made by means of microscopic examination of a skin snip. The subcutaneous nodule excised from one of the patients showed the adult Onchocerca volvulus. Both patients also had urinary schistosomiasis. The clinical features, laboratory findings, treatment and public health aspects of onchocerciasis are discussed.

Toxoplasma antibodies in immigrants from Hong Kong.
Seah SK.

Abstract
The sera of 200 Chinese adults recently immigrated to Canada from Hong Kong were examined for antibodies to Toxoplasma gondii by the indirect fluorescent antibody technique. It was found that the total incidence was 18.0%. This is significantly lower than that of the indigenous population of the same age groups in this area.