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Jinhua Bao, Hao Chen, Bjorn Drobe, Fan Lu; Working distance, distance variation and accommodative response during near work in Chinese Myopic Children. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3608.
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To investigate the working distance and accommodative response of myopic children during near vision tasks, and to delineate some of the factors affecting working distance.
We studied 110 myopic school children from Wenzhou, China. Accommodative responses were measured for the right eye of each subject using a Grand Seiko WV500 with the visual target (Maltese cross) 33 cm from the right eye, and near phoria was measured using the modified Thorington test. Working distances and variations for three near tasks (writing, reading, and hand-held video games playing) were measured with the Polhemus Fastrak system.
Children were accostumed to place their reading and writing material on a desk,but hold video games. Mean working distances were (23.0±5.5) cm when writing, (26.4±6.0) cm when reading, and (21.4±5.4) cm when playing game. Working distance showed significantly different among these three conditions (F=25.66, p<0.001). Mean working distance variations were (3.0±0.8) cm when writing, (3.3±10.0) cm when reading, and (1.6±1.9) cm when playing games. Distance variation showed significantly different between playing games and the other working conditions (p<0.001). Although accommodative lags were large (1.64D ± 0.61D), lag did not correlate with near phoria or working distance.
Chinese myopic children work at very close distances, especially when writing and playing hand-held video games. The visual distance was shortest and most stable while game-playing. Harmon distance played an important role when children worked with handheld material; however, accommodative lag and near phoria did not affect the working distance of myopic children. The relationship of working distance to reading proficiency and the induction of myopia have yet to be determined.
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