A comparison of seven visual fatigue assessment techniques in three data-acquisition VDT tasks

We compared 7 methods of measuring visual fatigue - accommodation power, vi sual acuity, pupil diameter, critical fusion frequency (CFF), eye movement velocity, subjective rating of visual fatigue, and task performance - for t heir sensitivity to visual load. In the experiment, 10 participants perform ed a monitoring task at 2 viewing distances, read articles under 2 levels o f screen contrast, and tracked visual targets at 2 different speeds. The sa me measurement techniques, excluding pupil diameter and eye movement veloci ty, were compared by extending the task time from 20 to 60 min with the sam e VDT tasks to test for possible improvement in sensitivity. The results in dicated that sensitivities of accommodation power, visual acuity, and CFF w ere greatly improved by a longer task period, but these 3 measurement techn iques did not distinguish among tasks. Pupil diameter, eye movement velocit y, and subjective rating of visual fatigue were sensitive in differentiatin g tracking from reading and monitoring tasks. Eye movement velocity and sub jective rating were sensitive to the changes in target velocity of the trac king task. Although task performance was not directly comparable to other m easurement techniques, it helped to ensure that participants maintained the same performance level by devoting more resources to the high-load conditi ons. Actual or potential applications of this research include using some o f these assessment techniques for the design of adaptive displays.