S K L Seah

Assessment of the Scleral Spur in Anterior Segment Optical Coherence Tomography Images

OBJECTIVEnTo assess visibility of the scleral spur in anterior segment optical coherence tomography (AS-OCT) images.nnnMETHODSnThis 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.nnnRESULTSnScleral 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).nnnCONCLUSIONSnThe 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.

Risk factors for nuclear, cortical and posterior subcapsular cataracts in the Chinese population of Singapore: the Tanjong Pagar Survey.

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

Education, socioeconomic status, and ocular dimensions in Chinese adults: the Tanjong Pagar Survey

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.

Determinants of Angle Closure in Older Singaporeans

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.

Defining "occludable" angles in population surveys: drainage angle width, peripheral anterior synechiae, and glaucomatous optic neuropathy in east Asian people.

OBJECTIVESnTo 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.nnnMETHODSnA 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.nnnRESULTSnThe 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.nnnCONCLUSIONSnIn 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.

Comparison of anterior chamber depth measurements using the IOLMaster, scanning peripheral anterior chamber depth analyser, and anterior segment optical coherence tomography

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° 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 (0u200a=u200aclosed to 4u200a=u200awide 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 ⩽ grade 2 (approximately 20°) 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.

The Singapore 5-Fluorouracil Trabeculectomy Study: Effects on Intraocular Pressure Control and Disease Progression at 3 Years

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) (pu200a=u200a0.0001); SPAC v IOLMaster, 0.027 (0.012) mm (−0.57 to 0.50 mm) (pu200a=u200a0.027). 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.

Intraocular pressure and visual field loss in primary angle closure and primary open angle glaucomas.

PURPOSEnTo 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.nnnDESIGNnProspective, randomized, double-blinded treatment trial.nnnPARTICIPANTSnTwo hundred forty-three Asian patients with primary open-angle or primary angle-closure glaucoma undergoing primary trabeculectomy.nnnMETHODSnOne eye of each patient was randomized to receive either intraoperative 5-FU or normal saline (placebo) during trabeculectomy.nnnMAIN OUTCOME MEASURESnPrimary 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.nnnRESULTSnOf 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).nnnCONCLUSIONSnThis 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.nnnFINANCIAL DISCLOSURE(S)nThe authors have no proprietary or commercial interest in any materials discussed in this article.

Initial Management of Acute Primary Angle Closure: A Randomized Trial Comparing Phacoemulsification with Laser Peripheral Iridotomy

Aim: To compare the correlation between visual field loss and the pretreatment intraocular pressure (IOP) in primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG). Methods: In a cross sectional observational study of 74 patients (43 PACG, 31 POAG), pretreatment IOP was measured at presentation, before treatment was initiated. The severity of visual field loss was assessed by AGIS score, mean deviation (MD), pattern standard deviation (PSD), and corrected pattern standard deviation (CPSD). Glaucomatous optic neuropathy was assessed from simultaneous stereo disc photographs. Results: There was a stronger correlation between pretreatment IOP and the extent of visual field loss in PACG subjects than in those with POAG for both MD (PACG: Pearson correlation coefficient (r) = 0.43, p = 0.002; r2 = 0.19), (POAG: r = 0.21, p = 0.13; r2 = 0.04) and AGIS score (PACG: r = 0.41, p = 0.003; r2 = 0.17), (POAG: r = 0.23, p = 0.19; r2 = 0.05 respectively). No such associations were seen for pattern standard deviation (PSD) or corrected pattern standard deviation (CPSD) in either group (p> 0.29). Both horizontal and vertical cup-disc ratio were well correlated with severity of field loss but not with presenting IOP for either diagnosis. Conclusions: This is consistent with the hypothesis of a greater IOP dependence for optic nerve damage in PACG than POAG and, conversely, a greater importance of other, less pressure dependent mechanisms in POAG compared to PACG.

Awareness of glaucoma, and health beliefs of patients suffering primary acute angle closure

PURPOSEnTo 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.nnnDESIGNnRandomized, controlled trial.nnnPARTICIPANTSnWe 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.nnnMAIN OUTCOME MEASURESnThe 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).nnnMETHODSnSubjects 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.nnnRESULTSnThere 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).nnnCONCLUSIONSnPerformed 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.