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B. Drobe, E. J. Seow, P. Koh, L. T. Yeoh; Working Distance in Bilingual Children: Is Chinese Text a Causal Factor for Myopia?. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3585. doi: https://doi.org/.
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Short working distances have been shown to induce faster myopia progression in children (Pärssinen O, et al. Br J Ophthalmol. 1989; 73: 547-551). The aim of this study is to determine if a shorter distance was present in children performing near work in Chinese as compared to roman letters and therefore, possibly explaining the higher prevalence of myopia in East Asian cities.
50 bilingual (English/Chinese) Singaporean Chinese children, 26 myopic (SE ≤ -0.50D) and 24 emmetropic (-0.50D < SE ≤ +0.50D), participated in this study. The children were divided into two age categories: age 7-8 (26) and age 10-11 (24) and into two gender groups (26 male, 24 female). All subjects performed 4 tasks in random order: writing and reading in Chinese and English on a desk while working distance was continuously recorded at 10 Hz by a Polhemus Fastrak system. Chair height was adjusted according to the height of each child. Results were analyzed in terms of working distance (WD) and relative working distance (RWD, working distance divided by forearm length).
Gender and ametropia had no effect on either WD or RWD (ANOVA, p>0.53), although a previous study showed that myopic Caucasian children had shorter relative working distances than emmetropic ones (Haro C, et al. Optom Vis Sci. 2000; 77 supp: 189). Shorter working distances were found for younger children (230±53mm vs. 269±63mm, ANOVA, p<0.01). This difference was no longer significant once data were normalized by forearm length (RWD, p=0.99). Writing tasks were performed significantly closer (p<0.001) than reading tasks for both WD (228±57mm vs. 270±57mm) and RWD (0.83±0.20 vs. 0.90±0.22). Neither the Chinese symbols nor the English alphabets had a difference in influence on WD or RWD (p>0.07). However, results showed both closer WD and RWD when reading English text as compared to Chinese (p<0.01).
Our results do not support the hypothesis that Chinese symbols induce shorter working distances as compared to a roman letters and as a consequence, a higher prevalence of myopia among the Chinese population.
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