Abstract
Visual symptoms are the most common complaints associated with prolonged computer use. We investigated effects of accommodation and vergence demands specified by the computer monitor viewing distance on the development of visual symptoms and visual function changes. Ten 18–35 year-old subjects performed a two-hour, visually demanding, text-viewing task at three viewing distances over three days. The visual angle of the character size was held constant. We measured changes in several static and dynamic properties of accommodation and binocular vision before and for 90 minutes after the viewing task. The 100 cm viewing distance induced less lead effect for accommodation to a distant target and less lag retention for accommodation to a near target. On the other hand, the viewing distance of 33 cm introduced less eye irritation or tearing symptoms and a higher overall dynamic convergence response compared to longer viewing distances. There were weak associations between changes in binocular functions and visual symptoms. While the symptoms were influenced by the viewing distance, they cannot be fully explained by the changes in the visual functions measured here.
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