Association of near work and dim light with myopia among 1400 school children in a district in North India

Purpose: The aim of this study was to determine the association of near work and dim light with myopia among school children in a district in North India. Methods: This study included a total of 1400 children of either sex studying in classes 5?10 in various schools of a district in North India, after taking consent from their guardians. Visual acuity was measured using Snellen’s chart. Myopes were called to our institute where wet retinoscopy was done and spectacles were prescribed. Results: There was a highly statistically significant correlation between myopia and increase in reading hours (P=0.001). There was a statistically significant correlation between myopia and >6hours of using mobile phones /week, more hours spent on using mobile phones correlated with an increased prevalence of myopia (P< 0.01). There was a statistically significant correlation between myopia and increasing hours of playing video games (P<0.01). We found a highly statistically significant positive correlation between the prevalence of myopia and reading in dim light (P=0.0006). Conclusion: There was a positive association between myopia and hours of doing near work. The prevalence of myopia increased with increased hours of doing near work (reading, playing video games and using mobile phones). The study showed a correlation between reading in dim light and myopia. Prevention of myopia may be possible by avoiding these risk factors.

Impact of Exposure to Dim Light at Night on Sleep in Female and Comparison with Male Subjects

OBJECTIVE: Light pollution has become a social and health issue. We performed an experimental study to investigate impact of dim light at night (dLAN) on sleep in female subjects, with measurement of salivary melatonin. METHODS: The 25 female subjects (Group A: 12; Group B: 13 subjects) underwent a nocturnal polysomnography (NPSG) session with no light (Night 1) followed by an NPSG session randomly assigned to two conditions (Group A: 5; Group B: 10 lux) during a whole night of sleep (Night 2). Salivary melatonin was measured before and after sleep on each night. For further investigation, the female and male subjects of our previous study were collected (48 subjects), and differences according to gender were compared. RESULTS: dLAN during sleep was significantly associated with decreased total sleep time (TST; F=4.818, p=0.039), sleep efficiency (SE; F=5.072, p=0.034), and Stage R latency (F=4.664, p=0.041) for female subjects, and decreased TST (F=14.971, p<0.001) and SE (F=7.687, p=0.008), and increased wake time after sleep onset (F=6.322, p=0.015) and Stage R (F=5.031, p=0.03), with a night-group interaction (F=4.579, p=0.038) for total sample. However, no significant melatonin changes. There was no significant gender difference of the impact of dLAN on sleep, showing the negative changes in the amount and quality of sleep and the increase in rapid eye movement (REM) sleep in the both gender group under 10 lux condition. CONCLUSION: We found a negative impact of exposure to dLAN on sleep in female as well as in merged subjects. REM sleep showed a pronounced increase under 10 lux than under 5 lux in merged subjects, suggesting the possibility of subtle influences of dLAN on REM sleep.

Horizontal and Vertical Fusional Amplitudes in Normal Eyes

Fusional amplitudes can be measured using various clinical techniques and targets. But the vergence ranges are different according to the used instruments and the environmental conditions. Currently, measurement with the prism is usually llsed but this method have wide vardabele ranges by the used targets and environmental settings. The authors measured the vertical and horizontal fusional amplitudes of 135 normal Korean men with rotary prism in a well-lit office and compared the group using dim light targer with the group using small letter target. In the group using dim light target, true far convergence value was 14.67 +/- 6.24 delta, true far divergence was 6.64 +/- 3.48 delta, true near convergence was 24.96 +/- 7. 33 delta, true near divergence was 11.05 +/- 5.13delta, far vertical vergence was 2.93 +/-0.95 delta, and near vertical vergence was 3.40 +/- 1.15 delta, There was no statistical differences among are groups(p>0.05), and between the groups using small letter target and dim light target in true near and far convergence amplitudes (p>0.05). This study shows that the method using dim light target is simple and valuable method in measuring the fusional vergences.