MONOCULAR IMPAIRMENT IN VIDEO DISPLAY TERMINAL OPERATORS A Case Series

This study examined the clinical findings of visual display terminal (VDT) users who presented with monocular symptoms. The sample consisted of 35 people performing sustained work at VDTs. Each subject underwent an evaluation that included: visual acuities, determination of refractive status, ocular motor testing, the stability of fixation, degree of suppressions of simultaneous binocular perception, and ocular health status. These findings were compared to a control group of 100 subjects who did not habitually use a VDT. Significant signs of unstable fixation/suppression were found with symptomatic subjects, as compared to the controls. We also found initial visual acuity differences between the two eyes of the VDT user group, but no significant refractive differences. Phoria measures were not significantly different between the two groups, but binocular fixation stability and suppression significantly predicted symptoms. The ergonomic analysis indicated that the various positionings of the VDT, keyboard and text could be a cause of the anomalous binocular responses. Symptoms and simultaneous perception measures reduced, or even returned to normal, when a recommended workstation layout was followed.