[Temporary myopia and subjective symptoms in video display terminal operators]

The study covered a group of female VDT operators assigned to data entry and data acquisition. Subjective VDT-related symptoms of asthenopia were assessed by means of a questionnaire. All operators were examined by an ophthalmologist. Visual acuity was measured using vision tables with optotypes. In order to achieve an objective assessment of VDT-induced visual fatigue, refractive power was measured at the beginning and at the end of the shift, using an infra-red autorefractometer. Changes in refractive power were then related to VDT work and asthenopia symptoms. Visual acuity defects were observed in 63.5% of the operators; in 36% of the cases the subjects were either unaware of the defects or the defects were not adequately corrected. 62.5% of the operators complained of subjective asthenopia symptoms. Asthenopia was not related to the number of hours at the VDT. The results suggest that ametropic subjects are likely to be more susceptible to visual fatigue than emmetropic subjects, since there was a tendency for the prevalence of asthenopia to increase in the former group. A significant decrease in refractive power (temporary myopization) was observed in 20% of the operators at the end of the shift at the VDT: all these subjects also complained of asthenopia, compared to 50% of the workers without end-of-shift myopization. The difference between the groups was highly significant (p less than 0.01); contrarywise, none of the subjects without asthenopia developed myopization. On the basis of these results, it can be concluded that end-of-shift myopization, as measured by an automatic refractometer, may be used as a reliable objective measurement of VDT-related visual fatigue.