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KMID : 1159320180200030241
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Korean Journal of Vision Science
2018 Volume.20 No. 3 p.241 ~ p.248
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Degradation in Legibility of English and Chinese Letters by Wearing of Progressive Addition Lenses
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Kwon Hae-In
Kim Dal-Young
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Abstract
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Purpose : Progressive additional lenses are being prescribed for short-sighted children to suppress the development of myopia. However, they are supposed to cause degradation in legibility of English and Chinese letters due to the narrow visual field of their intermediate zones. The purpose of this study is to compare the legibility of English and Chinese letters when readers wear progressive additional lenses to that when they wear single focus lenses.
Methods : A total of 40 subjects participated in this study. They were asked to find a designated letter as they read English or Chinese texts while wearing progressive additional lenses or single focus lenses. The length of time it took to read the given texts was measured, and the measurements were compared between wearing progressive additional lenses and wearing single focus lenses. The reading time was regarded as a criterion of legibility by the speed of reading method.
Results : The subjects took longer to read the texts when wearing progressive additional lenses than when wearing single focus lenses for both English and Chinese letters. Statistical significance was also observed in the case of the English letter ‘m’ and the Chinese letter ‘一’.
Conclusions : It was plausible that wearing progressive additional lenses resulted in longer reading time and degradation in legibility, due to the narrow visual field of the intermediate zone of progressive additional lenses. Such degradation of legibility could also lower readability and learning ability. Considering this, progressive additional lenses should be more carefully prescribed for short-sighted and school-aged children.
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KEYWORD
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Progressive Addition Lens , Legibility , Reading , Children
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