Accommodation Response in Observing CRT Display ―Measurements by means of Laser Optometer―

The present study was designed to examine the temporal courses of visual accommodaion response and contrast sensitivity(acuity) during prolonged display work. Five subjects continuously performed contrast resolution tests as the primary task, in which the contrast sensitivity for sinusoidal grating patterns on a CRT display placed at a distance of 38 cm was measured. During about 90 min experimental session, the accommodative distance while viewing the grating patterns was measured at intervals by means of a laser optometer, and each subject was required to inform his subjective fatigue symptoms. The results showad that accommodative distance and contrast sensitivity changed gradually from the initial leveal as a function of time course and exhibited the maximum deviation after approximately 30 and 50 min of the task, respectively, The change in accommodative distance showed individual difference in it's direction, however, presented a high correlation with that for contrast sensitivity. In accordance with these functional changes, the subjects reported visual fatigue symptoms such as blurred vision, difficulty of constant focusing, hardness of opening eyes, etc. These findings suggest that the changes in the accommodation system, detectable by means of laser optometer, could be used as an objective indicator of visual fatigue