Biomedical subjects

Wei-Han Chua

Publications and source records attributed to Wei-Han Chua.

10 recordsLinked to original sources

PubMed2006

Atropine for the treatment of childhood myopia.

PURPOSE: To evaluate the efficacy and safety of topical atropine, a nonselective muscarinic antagonist, in slowing the progression of myopia and ocular axial elongation in Asian children. DESIGN: Parallel-group, placebo-controlled, randomized, double-masked study. PARTICIPANTS: Four hundred children aged 6 to 12 years with refractive error of spherical equivalent -1.00 to -6.00 diopters (D) and astigmatism of -1.50 D or less. INTERVENTION: Participants were assigned with equal probability to receive either 1% atropine or vehicle eye drops once nightly for 2 years. Only 1 eye of each subject was chosen through randomization for treatment. MAIN OUTCOME MEASURES: The main efficacy outcome measures were change in spherical equivalent refraction as measured by cycloplegic autorefraction and change in ocular axial length as measured by ultrasonography. The primary safety outcome measure was the occurrence of adverse events. RESULTS: Three hundred forty-six (86.5%) children completed the 2-year study. After 2 years, the mean progression of myopia and of axial elongation in the placebo-treated control eyes was -1.20+/-0.69 D and 0.38+/-0.38 mm, respectively. In the atropine-treated eyes, myopia progression was only -0.28+/-0.92 D, whereas the axial length remained essentially unchanged compared with baseline (-0.02+/-0.35 mm). The differences in myopia progression and axial elongation between the 2 groups were -0.92 D (95% confidence interval, -1.10 to -0.77 D; P<0.001) and 0.40 mm (95% confidence interval, 0.35-0.45 mm; P<0.001), respectively. No serious adverse events related to atropine were reported. CONCLUSIONS: Topical atropine was well tolerated and effective in slowing the progression of low and moderate myopia and ocular axial elongation in Asian children.

Administration, Topical↗

PubMed2005

Prevalence of cataract in rural Indonesia.

PURPOSE: To describe the prevalence of cataract in adults in rural Sumatra, Indonesia. DESIGN: Population-based cross-sectional study. PARTICIPANTS: A random sample of all adults aged 21 years or older living in 3 rural villages in central Sumatra was assessed. Nine hundred nineteen of 1089 (84.4%) eligible adults participated. METHODS: A team of 7 ophthalmologists examined the anterior segment of both eyes using a portable slit lamp after pupil dilatation. Lens opacity was graded according to the Lens Opacities Classification System III (LOCS III). A structured questionnaire was used to collect data on education level and income. MAIN OUTCOME MEASURES: Cataract was defined as either a LOCS III nuclear region score of > or =4.0, cortical > or =4.0, or posterior subcapsular (PSC) cataract > or =2.0, in either eye. RESULTS: Two hundred one (21.9%) of 919 subjects were found to have cataract. The age-adjusted prevalence rate of cataract (including cataract surgery) was 23.0% (95% confidence interval, 20.8-25.2). The most common type of cataract for both genders (adjusted for age) was mixed (13%) followed by nuclear only (5.7%), and cortical only (4%). The prevalence rate of any cataract for adults aged 21 to 29 was 1.1%, increasing to 82.8% for those aged older than 60 years. Similar trends with age were noted for nuclear, cortical, and PSC cataract. Women had higher prevalence rates than men for all types of cataract except cortical. There was a trend of increasing prevalence of all types of cataract with decreasing education (P<0.001). CONCLUSIONS: Cataract prevalence in adults aged 21 years and older in rural Indonesia is among the highest reported in Southeast Asia. Despite this, there are inadequate resources available to manage this treatable disease. Allocation of resources to tackle the present burden of cataract would likely have large personal, social, and economic benefits.

Adult↗

PubMed2005

Myopia and associated pathological complications.

Besides the direct economic and social burden of myopia, associated ocular complications may lead to substantial visual loss. In several population and clinic-based cohorts, case-control and cross-sectional studies, higher risks of posterior subcapsular cataract, cortical and nuclear cataract in myopic patients were reported. Patients with high myopia (spherical equivalent at least -6.0 D) are more susceptible to ocular abnormalities. The prevalent risks of glaucoma were higher in myopic adults, and risks of chorioretinal abnormalities such as retinal detachment, chorioretinal atrophy and lacquer cracks increased with severity of myopia and greater axial length. Myopic adults were more likely to have tilted, rotated, and larger discs as well as other optic disc abnormalities. Often, these studies support possible associations between myopia and specific ocular complications, but we cannot infer causality because of limitations in study methodology. The detection and treatment of possible pathological ocular complications is essential in the management of high myopia. The ocular risks associated with myopia should not be underestimated and there is a public health need to prevent the onset or progression of myopia.

Adolescent↗

PubMed2005

Incidence and progression of myopia in Singaporean school children.

PURPOSE: To determine the incidence and progression rates of myopia in young Singaporean children. METHODS: A prospective cohort study, the Singapore Cohort Study of the Risk Factors for Myopia (SCORM), was conducted in two schools in Singapore (1999-2002). Children aged 7 to 9 years (n=981) were followed up over a 3-year period. Cycloplegic autorefraction and biometry parameter measures were performed annually, according to the same protocol. RESULTS: The 3-year cumulative incidence rates were 47.7% (95% confidence interval [CI]: 42.2-53.3), 38.4% (95% CI: 31.4-45.4), and 32.4% (95% CI: 21.8-43.1) for 7-, 8-, and 9-year-old children, respectively. The 3-year cumulative incidence rates were higher in Chinese (49.5% vs. 27.2%) and in 7-year-old compared with 9-year-old children at baseline (47.7% vs. 32.4%), though the latter relationship was of borderline significance after adjustment for race, gender, amount of reading (books/week), and parental myopia (P=0.057). Premyopic children with greater axial lengths, vitreous chamber depths, and thinner lenses were more prone to the development of myopia, after controlling for age, gender, race, reading, and parental myopia. The 3-year mean cumulative myopia progression rates were -2.40 D (95% CI: -2.57 to -2.22) in 7-year-old myopic children, -1.97 (95% CI: -2.16 to -1.78) in 8-year-olds, and -1.71 (95% CI: -1.98 to -1.44) in 9-year-olds. CONCLUSIONS: Both the incidence and progression rates of myopia are high in Singaporean children.

Age Distribution↗

PubMed2004

Optic disk and retinal characteristics in myopic children.

PURPOSE: To examine the baseline retina and optic disk characteristics in children. DESIGN: Cross-sectional study. METHODS: Subjects included 679 subjects with myopia and 100 with emmetropia, aged 8 to 13 years. Digital retina imaging and cycloplegic autorefraction were conducted to look for signs of retinal degeneration. Other outcome measures were vertical and horizontal cup-to-disk (CD) ratios, CD area ratio, parapapillary atrophy (PPA)-to-disk area ratio, and disk rotational angle. RESULTS: The prevalence of lattice degeneration was 0.15% (95% confidence interval: 0.008-1.00). No other retinal abnormalities were detected. Increased PPA-to-disk area ratio was associated with increased axial length, increased myopia severity, and increasing age. Cup-to-disk ratios were smaller in subjects with myopia compared with those with emmetropia, but this did not correlate with severity of myopia. In subjects with severe myopia, the upper pole of the disk was rotated away from the fovea but to lesser extent than in those with emmetropia or milder myopia. CONCLUSIONS: Apart from PPA, degenerative features were not commonly found in this study.

Adolescent↗

PubMed2004

Performance of the Hansatome microsuction ring for laser in situ keratomileusis in eyes with narrow palpebral apertures.

PURPOSE: To evaluate the performance of a new microsuction ring during laser in situ keratomileusis (LASIK) in eyes with narrow palpebral apertures. SETTING: Singapore National Eye Centre, Singapore, Republic of Singapore. METHODS: Laser in situ keratomileusis was performed sequentially in both eyes of 33 Chinese patients. A randomization table was used to determine the control and test eyes. A standard suction ring (20.3 mm diameter) was used in control eyes, and a microsuction ring (19.0 mm diameter) was used in test eyes. Corneal flaps were created using the Hansatome microkeratome (Baush & Lomb). The following ring performance parameters were evaluated: flap diameter deviation (actual minus nominal flap diameter), ease of suction ring application, adequacy of suction, and overall microkeratome performance. Parameters 2 to 4 were rated by the surgeons using a subjective 1 to 100 scale. RESULTS: The mean flap diameter deviation was 0.45 mm in the control eyes and 0.22 mm in the study eyes; the mean difference was 0.23 mm (95% confidence interval, 0.39-0.07) (P<.001). For ease of application, the mean score of the microsuction ring was 100 and of the standard suction ring, 89.9. For adequacy of suction, the mean score of the microsuction ring was 99.7 and of the standard suction ring score, 98.2 (P = .13). The mean overall microkeratome performance score using the microsuction ring was 99.4 and using the standard suction ring, 94.6 (P = .011). CONCLUSION: The Hansatome microsuction ring was easy to apply during LASIK in eyes with narrow palpebral apertures, and there appeared to be no compromise of ring performance and safety.

Adult↗

PubMed2004

Visual field loss from primary angle-closure glaucoma: a comparative study of symptomatic and asymptomatic disease.

PURPOSE: To assess the degree of visual field (VF) loss in subjects diagnosed with primary angle-closure glaucoma (PACG), and to compare the severity of such loss between those with symptomatic and asymptomatic disease. DESIGN: Observational case series. PARTICIPANTS: Seventy-six consecutive subjects with PACG who presented at a Singapore hospital. METHODS: Primary angle-closure glaucoma was defined as the presence of glaucomatous optic neuropathy and compatible VF loss associated with closed angles. There were 2 groups of subjects studied: group A consisted of those who presented with acute symptomatic angle closure, and group B consisted of those who were asymptomatic. Subjects underwent static automated threshold perimetry, and the first reliable VF was analyzed using the Advanced Glaucoma Intervention Study (AGIS) scoring system. The field tests were graded according to severity as mild, moderate, severe, and end-stage VF defects, based on AGIS scores of 0 to 5, 6 to 11, 12 to 17, and 18 to 20 respectively. MAIN OUTCOME MEASURES: Advanced Glaucoma Intervention Study scores of the first reliable threshold VF test. RESULTS: The mean age of study subjects was 61.4+/-9.6 years (range: 33-84), and the majority of subjects were female (59%) and Chinese (91%). In group A (n = 40), most eyes had mild or moderate VF defects (23 eyes [57.5%]), whereas 7 eyes (17.5%) had end-stage defects. This was in contrast to group B (n = 36), in which the majority of eyes had end-stage VF loss (19 eyes [52.8%]), with only 5 eyes (13.7%) having mild VF defects. Mean AGIS scores were 9.1+/-7.6 for group A and 14.2+/-6.9 for group B (P = 0.004). Cup-to-disc ratio was a significant predictor for VF loss, but age, gender, and level of presenting intraocular pressure were not correlated with VF outcome. CONCLUSIONS: Eyes with asymptomatic PACG often present with severe to end-stage VF loss at the time of first presentation to hospital. In contrast, most PACG eyes with previous symptomatic angle closure present with mild or moderate VF defects. The visual morbidity of PACG may be related to the finding that the asymptomatic form of the disease is visually destructive.

Acute Disease↗

PubMed2002

Sensitivity and specificity of visual acuity screening for refractive errors in school children.

PURPOSE: To examine the optimal cutoff point for the use of the visual acuity test to screen for refractive errors in schoolchildren. METHODS: In a sample of schoolchildren between 7 and 9 years old, visual acuity testing was performed using modified ETDRS charts monocularly without optical aids by trained personnel. Cycloplegic autorefraction was performed in each eye. The screening efficacy of using various cutoff points for referring children for further optometric/ ophthalmic assessment was studied. Myopia was defined as a spherical equivalent of at least -0.5 D, hyperopia a spherical equivalent of at least +2.0 D, and astigmatism a cylinder of at least -1.0 D in at least one eye. The sensitivity, specificity, and predictive values were calculated using each patient as a case; a receiver operator curve was plotted. RESULTS: A total of 1,028 children were tested. A satisfactory sensitivity/specificity profile was obtained using a referral criterion of visual acuity worse than or equal to 0.28 logarithm of the minimum angle of resolution in at least one eye. In this scenario, the sensitivity and specificity of this screening test were 72% (95% confidence interval [CI], 68 to 76) and 97% (95%CI, 95 to 98), respectively. The positive and negative predictive values were 96% (95%CI, 93 to 98) and 78% (95%CI, 75 to 82), respectively. CONCLUSIONS: The modified ETDRS visual acuity chart can be used to predict refractive errors in schoolchildren in Singapore in a sensitive and specific manner using a referral criterion of worse than or equal to 0.28 logarithm of the minimum angle of resolution.

Child↗

PubMed2002

Nearwork in early-onset myopia.

PURPOSE: To determine the relationship of nearwork and myopia in young elementary school-age children in Singapore. METHODS: A cross-sectional study of 1005 school children aged 7 to 9 years was conducted in two schools in Singapore. Cycloplegic autorefraction, keratometry, and biometry measurements were performed. In addition, the parents completed a detailed questionnaire on nearwork activity (books read per week, reading in hours per day and diopter hours [addition of three times reading, two times computer use, and two times video games use in hours per day]). Other risk factors, such as parental myopia, socioeconomic status, and light exposure history, were assessed. RESULTS: In addition to socioeconomic factors, several nearwork indices were associated with myopia in these young children. The multivariate adjusted odds ratio of higher myopia (at least -3.0 D) for children who read more than two books per week was 3.05 (95% confidence interval [CI], 1.80-5.18). However, the odds ratios of higher myopia for children who read more than 2 hours per day or with more than 8 diopter hours (1.50; 95% CI, 0.87-2.55 and 1.04; 95% CI, 0.61-1.78, respectively) were not significant, after controlling for several factors. CONCLUSIONS: Children aged 7 to 9 years with a greater current reading exposure were more likely to be myopic. This association of reading and myopia in a young age cohort was greater than the strength of the reading association generally found in older myopic subjects. Whether these results identify an association of early-onset myopia with nearwork activity or other potentially confounding factors is discussed.

Age Distribution↗

PubMed2002

Height and its relationship to refraction and biometry parameters in Singapore Chinese children.

PURPOSE: To examine the association between the anthropometric measurements of height, weight, body mass index (BMI) and refraction and other ocular parameters in Singapore Chinese children. METHODS: In a cross-sectional study of 1449 Chinese schoolchildren, aged 7 to 9 years, from three Singapore schools, height and weight were measured according to standard protocol, and BMI was calculated. Refractive error and corneal curvature measures were determined by autorefraction in eyes under cycloplegia. Axial length, vitreous chamber depth, lens thickness, and anterior chamber depth were measured using A-scan biometry ultrasonography. RESULTS: In comparison with the children with height in the first quartile for a given age and gender, the eyeball length in children in the fourth quartile was 0.46 mm longer, the vitreous chamber depth 0.46 mm deeper, the corneal radius of curvature 0.10 mm greater (i.e., flatter), refraction more negative by 0.47 D (-0.76 D versus -0.29 D), and axial length-to-corneal curvature radius (AL-CR) ratio higher, after analyses controlling for age, gender, parental myopia, reading, school, and weight. The associations of height with refractive error and AL-CR ratio were significant in girls but not in boys. Heavier and more obese children had refractions that were more hyperopic (P = 0.01, P = 0.08), after analyses controlling for age, gender, parental myopia, reading, and school (height was also controlled for if weight was evaluated). This association was present in boys but not in girls. CONCLUSIONS: Controlling for age, gender, parental myopia, reading, school, and weight showed that taller Singapore Chinese children had eyes with longer axial lengths, deeper vitreous chambers, flatter corneas, and refractions that tended toward myopia. In multivariate analysis, eyes in children who were heavier or who had a higher BMI tended to have refractions that were more hyperopic, and eyes in heavier children had shorter vitreous chambers. Differences between the present results and a recent report in Singapore adults suggest either a cohort effect or a potential influence of systemic endocrine or metabolic factors during childhood on refractive development.

Biometry↗