[The McCollough effect and visual fatigue induced by the use of green phosphorus monochromatic video terminals]

We examined 101 students (40 men, 61 women) aged 16-19 years, working 1-3 hours daily with video display terminals (VDT) with luminous green characters on dark background. McCollough visual aftereffect (ME) was reported, almost occasionally, in 80.2% of the examined group. 68% of the students referred daily ME appearance. Usually the effect appeared after 1 hour or less of VDT work and might persist for 1 hour or more. ME prevalence and persistence were significantly greater in women than in men. Apparently no relations were observed between ME prevalence and VDT work hours of visual defects. ME prevalence and persistence were significantly related to VDT induced visual asthenopia symptoms, but not with ocular asthenopia. According to our results, ME appearance may represent an early index of individual susceptibility to visual asthenopia induced by green characters VDT and/or be itself a precocious visual asthenopia symptom.