Visual comfort in VDT workstation design.

This study aims to give recommendations for a comfortable visual display terminal (VDT) workstation design by investigating physiological resting states of the eye in 3 experiments. Dark vergence, in experiment 1, was evaluated to be at a distance of about 50 cm from the eye as an average of 14 subjects. Dark vergence was found to shift farther with an upward gaze while a nearer shift occurred with a downward gaze. In experiment 2, the average dark focus for 11 subjects was found to be 1.4 diopters (D) or a distance of about 74 cm from the eye. Experiment 3 ascertained the superiority of a positive display polarity (dark characters on a bright background) under 500 1x illuminated level, by using pupil size analysis in 10 subjects. The ergonomic recommendations for a VDT workstation obtained in this study are a positive display polarity under regular lighting condition, a downward gaze, and a viewing distance between 50 and 70 cm.