VDT work, oculomotor strain, and subjective complaints: an experimental and clinical study.

Two studies, one experimental and one clinical, are presented. Study I examines the effect of three hours of continuous VDT work (text-editing) on a set of optometric and health-related variables in an experimental design with two matched groups, one experimental (n = 18) and one control group (n = 19). Doing the same keyboard activities for 3 h as the experimental group, the control group was looking out of a window instead of at the display while working (distance viewing). There were significant group differences in work related effects on the eyes' ciliary and extraocular muscles and on subjective symptoms, indicating that not only visual symptoms but also muscle pain in the head, neck, and upper back regions may result from near-point induced oculomotor strain. Study II shows the health effect of optical corrections on symptomatic VDT workers (n = 14). There is a significant pre-post reduction in symptoms, indicating that visual anomalies contribute to work-related symptoms. The results of both studies are discussed in a visual ecological perspective.