[Effects of visual and mental strain on VDT (visual display terminal) performance]

The progression of visual and mental strain in VDT work was investigated through an experimentally-designed VDT task providing a number of stressors including pacing, repetition, judgment and output decisions. We measured the effects of CFF (critical fusion frequency), TAF (the ability to maintain concentration), EEG (electroencephalogram) and near-point accommodation of various changes in the duration of the testing period. The subjects were seven male university students who performed single multiplication problems at a rate of 60 per minute. The problems were presented to them on a CRT screen and on paper for periods of 90 min each. The results obtained were as follows; CFF values and near-point accommodation of VDT performance were significantly decreased compared to Non-VDT's as a control. The TAF test showed that the mental strain in a VDT task is greater than that in a Non-VDT task. CFF values of VDT performance showed a tendency to decline in the 30th min after commencement, but in the 60th min and thereafter a significant lowering was noticed. In TAF and near-point accommodation of VDT performance, the greatest decline was in the 60th min, and this was significantly reduced only immediately after the work period. CFF values and near-point accommodation were not recovered after 60 min from the end of a 90 min VDT task. However, TAF X L values recovered in the 30th min after VDT performance. The peak level of alpha waves from the parietal region moved toward the slow alpha band with the elapse of VDT task time, but returned [or reverted] to the initial state 30 min after the test period ended.