Wan-Ling Wong

Prevalence and Risk Factors for Refractive Errors in the Singapore Malay Eye Survey

PURPOSE To describe the prevalence and risk factors for myopia and other refractive errors in an urban Malay population in Singapore. DESIGN Population-based, cross-sectional study. PARTICIPANTS Persons of Malay ethnicity, between 40 and 80 years of age, living in Singapore. METHODS Refractive error was determined by subjective refraction and if unavailable by autorefraction. Data were analyzed for 2974 adults without previous cataract surgery and who had right eye refraction data. Risk factor data, such as education levels and near work activity, were obtained from a face-to-face interview. MAIN OUTCOME MEASURES Myopia, defined as spherical equivalent (SE) refraction less than -0.5 diopters (D), astigmatism as cylinder less than -0.5 D, hyperopia as SE greater than 0.5 D, and anisometropia as the difference in SE greater than 1.0 D. RESULTS The prevalence of myopia in the right eye was 30.7% (9.4% unilateral myopia and 21.3% bilateral myopia), the prevalence of astigmatism in the right eye was 33.3% (95% confidence interval [CI, 33.0-33.5), the prevalence of hyperopia in the right eye was 27.4% (95% CI, 24.7-27.6), and the prevalence of anisometropia was 9.9% (95% CI, 9.7-10.0). There was a U-shaped relationship between increasing age and the prevalence of myopia, which was partially explained by the age-related increase in the prevalence of cataract. In a multiple logistic regression model, female sex, age, higher educational level, and cataract were associated with myopia. Adults with myopia were more likely to have astigmatism (P<0.001) in multivariate analyses. CONCLUSIONS A quarter of older adult Malay people in Singapore had myopia. Compared with previous reports of similarly aged Singapore Chinese adults, the prevalence of myopia, astigmatism, and anisometropia was lower, whereas the prevalence of hyperopia was similar.

Atropine for the treatment of childhood myopia: safety and efficacy of 0.5%, 0.1%, and 0.01% doses (Atropine for the Treatment of Myopia 2).

PURPOSE Our previous study, Atropine for the Treatment of Myopia 1 (ATOM1), showed that atropine 1% eyedrops were effective in controlling myopic progression but with visual side effects resulting from cycloplegia and mydriasis. The aim of this study was to compare efficacy and visual side effects of 3 lower doses of atropine: 0.5%, 0.1%, and 0.01%. DESIGN Single-center, double-masked, randomized study. PARTICIPANTS A total of 400 children aged 6-12 years with myopia of at least -2.0 diopters (D) and astigmatism of -1.50 D or less. INTERVENTION Children were randomly assigned in a 2:2:1 ratio to 0.5%, 0.1%, and 0.01% atropine to be administered once nightly to both eyes for 2 years. Cycloplegic refraction, axial length, accommodation amplitude, pupil diameter, and visual acuity were noted at baseline, 2 weeks, and then every 4 months for 2 years. MAIN OUTCOME MEASURES Myopia progression at 2 years. Changes were noted and differences between groups were compared using the Huber-White robust standard error to allow for data clustering of 2 eyes per person. RESULTS The mean myopia progression at 2 years was -0.30±0.60, -0.38±0.60, and -0.49±0.63 D in the atropine 0.5%, 0.1%, and 0.01% groups, respectively (P=0.02 between the 0.01% and 0.5% groups; between other concentrations P > 0.05). In comparison, myopia progression in ATOM1 was -1.20±0.69 D in the placebo group and -0.28±0.92 D in the atropine 1% group. The mean increase in axial length was 0.27±0.25, 0.28±0.28, and 0.41±0.32 mm in the 0.5%, 0.1%, and 0.01% groups, respectively (P < 0.01 between the 0.01% and 0.1% groups and between the 0.01% and 0.5% groups). However, differences in myopia progression (0.19 D) and axial length change (0.14 mm) between groups were small and clinically insignificant. Atropine 0.01% had a negligible effect on accommodation and pupil size, and no effect on near visual acuity. Allergic conjunctivitis and dermatitis were the most common adverse effect noted, with 16 cases in the 0.1% and 0.5% atropine groups, and no cases in the 0.01% group. CONCLUSIONS Atropine 0.01% has minimal side effects compared with atropine at 0.1% and 0.5%, and retains comparable efficacy in controlling myopia progression.

Prevalence and Causes of Low Vision and Blindness in an Urban Malay Population: The Singapore Malay Eye Study

OBJECTIVE To describe the prevalence and causes of low vision and blindness in a Malay population. METHODS A population-based, cross-sectional study of 3280 participants of Malay ethnicity, aged 40 to 79 years, was conducted. Participants underwent standardized ophthalmic assessments to determine (1) presenting and best-corrected visual acuity according to US and modified World Health Organization definitions of blindness and low vision and (2) the primary causes of visual impairment. RESULTS Of 4168 eligible individuals, 3280 participated in the study (78.7%). The population-weighted prevalence of bilateral blindness was 0.3% and of bilateral low vision, 4.4% (US definition of presenting visual acuity). After best-corrected visual acuity, the population-weighted prevalence of bilateral blindness was reduced to 0.1% and bilateral low vision to 1.0%. Cataract was the main cause of presenting unilateral (38.9%) and bilateral (65.2%) blindness, whereas undercorrected refractive error was the main cause of presenting unilateral (68.8%) and bilateral (52.2%) low vision. Diabetic retinopathy, age-related macular degeneration, and glaucoma were the other leading causes of blindness and low vision. CONCLUSIONS The age-standardized prevalences of bilateral blindness and low vision in a Malay population were lower when compared with other Asian studies. Undercorrected refractive error and cataract are the leading causes of visual impairment among the Malay adult population in Singapore.

Prevalence and Causes of Visual Impairment and Blindness in an Urban Indian Population: The Singapore Indian Eye Study

PURPOSE To describe the prevalence and causes of visual impairment and blindness in an urban Indian population. DESIGN Population-based study. PARTICIPANTS Ethnic Indians aged more than 40 years living in Singapore. METHODS Participants underwent standardized ophthalmic assessments for visual impairment and blindness, defined using best-corrected visual acuity (BCVA) and presenting visual acuity (PVA), according to US and modified World Health Organization (WHO) definitions. MAIN OUTCOME MEASURES Unilateral visual impairment or blindness was defined on the basis of the worse eye, and bilateral visual impairment or blindness was defined on the basis of the better eye. Primary causes of visual impairment were determined. RESULTS A total of 3400 eligible individuals (75.6% response rate) participated. On the basis of US definitions, the age-standardized prevalence was 0.4% for bilateral blindness (≤20/200, better eye) and 3.4% for bilateral visual impairment (<20/40 to >20/200, better eye). Another 0.3% of bilateral blindness and 13.4% of bilateral visual impairment were correctable with refraction. Cataract was the principal cause of best-corrected bilateral blindness (60.0%) and bilateral visual impairment (65.7%). Other major causes of blindness and visual impairment included diabetic retinopathy, age-related macular degeneration, glaucoma, corneal opacity, and myopic maculopathy. CONCLUSIONS The prevalence of bilateral blindness and visual impairment in Indians living in Singapore is lower than estimates from populations living in India, but similar to estimates obtained from Singapore Malay and Chinese populations. Cataract is the leading cause of blindness and visual impairment. One in 20 cases of bilateral blindness and 1 in 10 cases of bilateral visual impairment are attributable to diabetic retinopathy. These data may have relevance to many ethnic Indian persons living outside India.

Determinants of ganglion cell-inner plexiform layer thickness measured by high-definition optical coherence tomography.

PURPOSE To determine the distribution, variation, and determinants of ganglion cell-inner plexiform layer (GC-IPL) thickness in nonglaucomatous eyes measured by high-definition optical coherence tomography (HD-OCT). METHODS Six hundred twenty-three Chinese adults aged 40 to 80 years were consecutively recruited from a population-based study. All subjects underwent a standardized interview, ophthalmic examination, and automated perimetry. HD-OCT with macular cube protocol was used to measure the GC-IPL thickness. Univariate and multiple linear regression analyses were performed to examine the relationship between GC-IPL thickness with ocular and systemic factors. RESULTS The mean (±SD) age of study subjects was 52.84 ± 6.14 years, 50.1% were male, and all subjects had normal visual fields with no signs of glaucoma or glaucoma suspect. The mean overall, minimum, superior, and inferior GC-IPL thicknesses were 82.78 ± 7.01 μm, 79.67 ± 9.17 μm, 83.30 ± 7.89 μm, and 80.16 ± 8.31 μm, respectively. In multiple linear regression analysis, GC-IPL thickness was significantly associated with age (β = -0.202, P < 0.001), female sex (β = -2.367, P < 0.001), axial length (β = -1.279, P = 0.002), and mean peripapillary retinal nerve fiber layer (RNFL) thickness (β = 0.337, P < 0.001). IOP, central corneal thickness, disc area, serum glucose level, and history of diabetes mellitus had no significant influence on GC-IPL thickness. CONCLUSIONS Thinner GC-IPL was independently associated with older age, female sex, longer axial length, and thinner RNFL thickness. These factors should be taken into account when interpreting GC-IPL thickness measurements with HD-OCT for glaucoma assessment.

Determinants of Corneal Biomechanical Properties in an Adult Chinese Population

PURPOSE To investigate variations in corneal hysteresis (CH) and corneal resistance factor (CRF) and their ocular and systemic associations in Chinese adults. DESIGN Population-based, cross-sectional study. PARTICIPANTS We included 1136 subjects of Chinese origin from an ongoing population-based study. METHODS All subjects in this population-based study underwent a standardized ocular examination including keratometry (corneal radius of curvature), intraocular pressure (IOP) measurement with Goldmann applanation tonometry, central corneal thickness (CCT), and axial length (AL) assessments. The CH and CRF were measured with the Ocular Response Analyzer. Participants underwent a detailed interview and laboratory investigations that included estimation of nonfasting serum glucose, glycosylated hemoglobin, and lipid profile. MAIN OUTCOME MEASURES We assessed CH, CRF, and their associations with demographic, ocular, and systemic factors. RESULTS The mean age of study subjects was 55.3±8.4 years and 51.2% were females. The mean CH and CRF were 10.6±1.5 and 10.1±1.6 mmHg, respectively. Women had higher mean CH (10.8 vs 10.4 mmHg; P<0.001) and CRF (10.4 vs. 9.8 mmHg; P<0.001) than men. After adjusting for age, gender, IOP, CCT, keratometry, AL, and diabetes, CH was negatively associated with age (β = -0.034; P<0.001), IOP (β = -0.037; P = 0.01), corneal radius of curvature (β = -0.963; P<0.001), and AL (β = -0.106; P = 0.001); and positively associated with female gender (β = 0.308; P<0.001) and CCT (β = 0.020; P<0.001). The CRF showed a negative association with age (β = -0.023; P<0.001) and corneal radius of curvature (β = -0.771; P<0.001), and was positively associated with female gender (β = 0.368; P<0.001), IOP (β = 0.134; P<0.001) and CCT (β = 0.024; P<0.001). Subjects with diabetes had a higher CH (β = 0.324; P<0.001) and CRF (β = 0.396; P = 0.002) compared with those without diabetes. CONCLUSIONS With advancing age, the CH and CRF in adult Chinese decreased. Women and subjects with diabetes had greater CH and CRF. Corneal biomechanical properties of hysteresis and resistance factor are significantly influenced by IOP, CCT, corneal radius of curvature, and AL.

Intravitreal Triamcinolone Prior to Laser Treatment of Diabetic Macular Edema: 24-Month Results of a Randomized Controlled Trial

PURPOSE To report the 24 months outcomes from a clinical trial of intravitreal triamcinolone acetonide (IVTA) plus laser versus laser treatment only in eyes with diabetic macular edema (DME). DESIGN Prospective, double-masked, randomized, placebo-controlled study. PARTICIPANTS Eighty-four eyes of 54 participants were entered into the study, with 42 eyes randomly assigned to receive IVTA plus laser and 42 randomly assigned to receive laser treatment alone. Primary end point data were available for 71 (84.5%) eyes at 24 months, with last visual acuity observation carried forward for the remaining eyes. METHODS Best-corrected logarithm of minimum angle of resolution (logMAR) visual acuity and central macular thickness (CMT) by optical coherence tomography were measured after laser treatment preceded by either IVTA or sham. MAIN OUTCOMES MEASURES The primary outcome was the proportion of eyes with improvement in visual acuity of 10 letters or more at 24 months. The secondary outcomes were mean visual acuity, requirement for further treatment, change in CMT, and adverse events. RESULTS At 24 months, improvement of 10 logMAR letters or more was seen in 15 (36%) of 42 eyes treated with IVTA plus laser compared with 7 (17%) of 42 eyes treated with laser only (P = 0.047; odds ratio, 2.79; 95% confidence interval, 1.01-7.67). There was no difference in the mean CMT or mean logMAR visual acuity between 2 groups. At least 1 retreatment was required in the second year of the study in 29 (69%) of 42 IVTA plus laser-treated eyes compared with 19 (45%) of 42 laser only eyes (P = 0.187). Cataracts were removed from 17 (61%) of 28 phakic IVTA plus laser-treated eyes versus 0 (0%) of 27 laser only eyes (P<0.001). Treatment for elevated intraocular pressure was required in 27 (64%) of 42 IVTA plus laser eyes compared with 10 (24%) of 42 laser only eyes (P<0.001). CONCLUSIONS Treatment with IVTA plus laser resulted in a doubling of improvement in vision by 10 letters or more compared with laser only over 2 years in eyes with DME, but is associated with cataract and raised intraocular pressure.

Quantitative evaluation of anterior chamber parameters using anterior segment optical coherence tomography in primary angle closure mechanisms

Background:  To evaluate different mechanisms of primary angle closure and to quantify anterior chamber parameters in these mechanisms using anterior segment optical coherence tomography in an Asian population.

Prevalence of and Racial Differences in Pterygium A Multiethnic Population Study in Asians

PURPOSE To describe the prevalence and risk factors of pterygium in a multiethnic Asian population and to examine racial differences. DESIGN Population-based study in Singapore, located 1° north of the equator. PARTICIPANTS Data were analyzed from 8906 participants from 3 population-based studies of Malays, Indians, and Chinese persons 40 years of age and older conducted between 2004 and 2011. METHODS Standardized slit-lamp examinations were performed by trained study ophthalmologists to examine the anterior segment for evidence of pterygium. Every subject underwent standardized systemic and ocular examinations, interviewer-administered questionnaires, and blood investigations for risk factor assessment. Regression and principle component analysis models were constructed to study the relationship of race and other factors to pterygium. MAIN OUTCOME MEASURES Any pterygium and severe (grade 3 or opaque) pterygium. RESULTS The overall prevalence of any pterygium was 10.1% (n = 900), of which severe pterygium was seen in 1.6% (n = 142). The prevalence of any pterygium was more common in Malays (15.5%) than Chinese (7.0%; P<0.001) or Indians (7.0%; P<0.001). Multivariate analysis revealed increasing age (P<0.001), male gender (P<0.001), Malay race (P<0.001), and having a poorer education level (P<0.001) as significant factors for any pterygium. Race contributed significantly to presence of any pterygium (41%; P<0.001) or presence in both eyes (33%; P<0.001) compared with other risk factors. Severe pterygium was associated with outdoor occupation (P = 0.02), but race was not a significant risk factor in multivariate analysis. CONCLUSIONS This population-based study in Asian persons of different races living in the same geographical location at the equator indicated that race is a significant risk factor for pterygium, with Malays having higher prevalence than Indians and Chinese, while controlling for other risk factors.

Racial Differences in the Prevalence of Diabetes but Not Diabetic Retinopathy in a Multi-ethnic Asian Population

PURPOSE To compare the prevalence and risk factors of diabetes (DM) and diabetic retinopathy (DR) in a multi-ethnic Asian population of Chinese, Malays, and Indians in Singapore. METHODS A total of 2919 individuals participated in a population-based, cross-sectional study in Singapore of Chinese (n = 1633), Malays (n = 658), and Indians (n = 628) aged 40 to 95 years, with retinal photographs, graded using the Early Treatment Diabetic Retinopathy Study (ETDRS) severity scale. DM was defined as fasting plasma glucose ≥ 7 mmol/L, self-reported physician-diagnosed diabetes, and use of glucose-lowering medication. RESULTS The overall age-standardized prevalence of diabetes was 13.8% (Chinese, 11.5%; Malays, 17.1%; and Indians, 21.6%; P < 0.0001). Among persons with diabetes (n = 401), the overall age-standardized prevalence of DR was 25.4% (20.1%, 24.8%, and 28.9% in Chinese, Malays, and Indians, respectively; P = 0.290). In multivariate analysis, longer diabetes duration (odds ratio [OR], 1.05; 95% confidence interval [CI], 1.01-1.09, per year increase), higher glycated hemoglobin (OR 1.25; 95% CI, 1.01-1.54, per 1% increase), and serum creatinine levels (OR, 1.01; 95% CI, 1.00-1.03, per mg/dL increase) were the independent risk factors of DR in the whole population. Race was not found to be associated with DR (OR, 1.35; CI, 1.00-1.83). The associations of major risk factors with DR were similar among the three ethnic groups. CONCLUSIONS There was a significant difference in the prevalence of diabetes between Chinese, Malays, and Indians. The main risk factors of DR, similar among the three ethnic groups, are longer diabetes duration, higher hbA1c, and higher creatinine levels. No significant racial differences were found in the prevalence of DR among persons with diabetes.