Hui-Min Wu

Academic achievement, close up work parameters, and myopia in Singapore military conscripts

AIM To determine the relation of refractive error to environmental factors, including close up work, in Singapore military conscripts. METHODS A cross sectional study was conducted on 429 Singapore military conscripts. Non-cycloplegic refraction and A-scan biometry were performed in both eyes. A detailed questionnaire was administered by in-person interview to obtain information about current and past near work activity, extra tuition lessons, educational experiences, and family demographics. RESULTS Myopia associated with the conscript having been educated in the (gifted, special, or express) educational streams (adjusted odds ratio (OR) = 3.8, 95% confidence interval CI 2.0–7.3), and having completed pre-university education (OR=4.1, 95% CI 1.9–8.8). The reported close up work activity at age 7 years did correlate with age of onset of myopia (p<0.001). In parallel, supplemental tuition lessons in primary school has (OR=2.6, 95% CI 1.4–4.9) associated with conscript myopia. Parental myopia was positively associated with myopia (p<0.001), but this relation disappeared when adjusted for environmental factors. Current (p=0.83) and past close up work activity at age 7 years (p=0.13) did not correlate with myopia. CONCLUSION Educational level and educational stream positively related to myopia. A relation was observed with reported close up work activity in early childhood and with tuition classes during elementary school, but not with current close up work activity. These results underscore the strong influence of environment in myopia pathogenesis but a role for close up work activity remains indeterminate.

Prevalence rates and epidemiological risk factors for astigmatism in Singapore school children.

Purpose. This study examined the prevalence rate of astigmatism and its epidemiological risk factors in Singapore school children. Methods. In a study of school children aged 7 to 9 years old in two schools in Singapore in 1999, a detailed questionnaire was administered to parents regarding reading or close-work habits, past history of close-work, family history, and socioeconomic factors. Cycloplegic refraction was performed five times in each eye. Defining astigmatism as worse than or equal to 0.5, 0.75, and 1 D cylinder in the right eye, the prevalence of astigmatism was calculated. Results. The study population consisted of 1028 children. The prevalence rate of astigmatism (worse than or equal to 1 D cylinder) was 19.2% (95% confidence interval, 16.8 to 21.6). This was not different between genders, ethnic groups, or age (p > 0.05). With-the-rule astigmatism was more common than against-the-rule astigmatism. The prevalence of astigmatism and myopia was 9.8% (95% confidence interval, 8.0 to 11.6). A high AC/A ratio was associated (p = 0.003) with astigmatism, even after exclusion of myopic children. On vectorial analysis, J0 and J45 were associated with the number of hours of playing video games, whereas J45 was also associated with computer use. Only J45 was associated to male gender, a high AC/A ratio, and a family history of myopia. Conclusions. The prevalence rate of astigmatism (≥1 D) was 19%. Playing video games and computer use may be associated with astigmatism severity, although the presence of astigmatism (≥1 D) was not associated with any nearwork factors. A family history of myopia was associated with oblique astigmatism severity. A high AC/A ratio is associated with astigmatism, and this requires further investigation.

Automated static perimetry : the influence of myopia and its method of correction

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.

Myopia and night lighting in children in Singapore

AIM To examine the role of night time lighting and myopia in children in Singapore METHODS A cross sectional study was conducted on 1001 children in two Singapore schools. Cycloplegic refraction and A-scan biometry measurements were made in both eyes. A detailed questionnaire was completed by the parents to obtain information on night time lighting, near work activity, educational and demographic factors. RESULTS There was no difference in myopia prevalence rates in children exposed to night time light (33.1%) compared with children who slept in the dark (31.4%) before age 2. In addition, vitreous chamber depth was not related to night light (p=0.58) before age 2. These results remained even after controlling for near work. CONCLUSION Myopia is not associated with night light in Asian populations.

Haplotypes of the β2-adrenergic receptor gene are associated with essential hypertension in a Singaporean Chinese population

Objective To investigate the relation between the gene encoding the β2-adrenergic receptor (B2AR) and essential hypertension in a Singaporean Chinese cohort. Methods Three single nucleotide polymorphisms (SNPs) were genotyped in 190 cases and 323 controls, and eight haplotypes were determined and tested for association using the likelihood test statistic. Results We observed a significant difference in haplotype frequency distributions between the cases and the controls (P < 0.00001). A logistic regression model fitted to the data supported this finding. Conclusion The results suggest that variants at the B2AR locus may play a role in the pathophysiology of hypertension in this population.

Heterozygosities and allelic frequencies of a set of microsatellite markers used for genome-wide scans in a Chinese population

AbstractMicrosatellite (short tandem repeat) markers are useful tools for genetic linkage analysis because of their high frequency of occurrence in eukaryotic genomes, ease of typing, and high polymorphism content. To establish a panel of microsatellite markers useful for genome-wide screens in the Chinese population, we determined the heterozygosities and allelic frequencies of a widely used set of 285 markers in 208 individuals of Han Chinese descent. Although the median heterozygosity level in our Chinese population was 0.72, only 63.6% of these markers have a heterozygosity of at least 0.7, compared with 90.8% in the original Caucasian sample. The significant difference in heterozygosity and allelic frequencies between populations suggests that markers should be optimally selected for each study population to maximize information content and power.