[An experimental study of work load on VDT performance. Part 1. Effects of polarity of screen and color of display].

Study were made on the effects of polarity of screen and color of display on work load of VDT tasks. The subjects of the present experiment were eight healthy male college students (age: 21-23 yr) having a naked binocular vision of not less than 0.7 and no astigmatism nor hyperopia. The test consisted of an experimental word processing task in which the subjects visually searched e's in given sequences of alphabetical letters displayed on the CRT and converted them to 5's through keyboard operation. As for experimental conditions, four levels of screen image, that is, positive and negative screens and green and white colored displays were adopted and 2 hr were given for each operation time. Critical flicker fusion (CFF), near point distance, accommodation time, subjective fatigue symptoms, heart rate, electromyogram in upper limbs and performance score were measured. The following results were obtained. Decrease in C.F.F. and extension of near point distance were observed in all experimental conditions during the operating time. Increase in complaints of subjective fatigue related to visual function was observed in all experimental conditions after two hour VDT task. Greater extension of near point distance and larger complaints of subjective fatigue were observed in subjects using the green colored display than in those using the white colored display. This suggests that the visual load using the green colored display is larger than that using the white colored display. A larger decreased in C.F.F. and greater complaints of subjective fatigue were demonstrated in subjects using negative screen than those using positive screen. This suggests that the visual load using the negative screen is larger than that using the positive screen.