RESUMEN
UNLABELLED: Since the 70's the occupational use of electronic systems equipped with visual display terminals (VDTs) became wide-spread also in Italy. Some longitudinal studies on large samples of VDT workers found no significant changes of myopia (M) with regard to years and daily hours spent working at a VDT. OBJECTIVE: To evaluate the prevalence and the time course of M in 209 VDT workers employed in the service sector. MATERIALS AND METHODS: After obtaining workers' informed consent their work, social, family and personal medical histories were collected. Myopia was defined as need of >0.25 D negative spherical correction. Average daily hours duringfollow-up and overall years spent working at a VDT were calculated as exposure indexes. RESULTS: The mean baseline age was 39.2 years (SD: 8.7, min-max: 22-62) and the mean education was 14 years (SD: 2.2). The mean follow-up period was 5.5 (3-9) years. The prevalence of M was 45.5% at the start and 49.8% at the end of the study. It was higher in workers with >13 years of education and in those < 40 year-old. A slight but significant increase of the degree of M (dioptres) occurred during the follow-up. The change in the degree of M was not different between the classes of VDT exposure (< or = 4 and >4 daily hours; < or =15 and >15 years spent), of education and of age at the end of follow-up. DISCUSSION: The high mean educational level can partly explain the higher prevalence of M detected in the workers on study with respect to the one described elsewhere on VDT workers and general population. The progression of the M seems not to be related to the professional and personal variables analyzed, but to depend on the natural evolution of M. Further studies are needed to confirm these preliminary data in larger groups of VDT workers.