The effect of crowding in smartphone and printed materials on accommodative response and lag of accommodation

Abstract

This study aimed to investigate the effect of crowding letters in smartphone and printed reading materials on accommodative response and lag of accommodation. The effect of crowding letters presented in printed reading material and smartphone were uncrowded target A (two letter width letter separation), uncrowded target B (reading material with standard letter separation) and crowded target C (reading material with abutting letter) at viewing distances of 33 cm, 40 cm and 50 cm corresponding to the accommodative stimulus of 3.00 D, 2.50 D and 2.00 D. Accommodative response was found increased significantly with closer viewing distances, regardless of crowded or uncrowded target. Printed materials showed significantly higher accommodative response in all distances compared to smartphone. There were no significant differences for both reading materials at 50cm. Changes in the accommodation lag showed statistically higher as accommodation demand increased for uncrowded target A (smartphone). There were no significant changes in the lag of accommodation regardless of targets and distances between smartphone and printed material. These findings suggested that the smartphone reading materials produced lesser accommodative response than printed. Smaller changes of accommodative lag seem to prevent visual fatigue with closer working distance in both smartphone and printed material. Key Words: accommodation, accommodation response, accommodative lag, crowding, near target, viewing distance