RESUMEN
PURPOSE: This study assessed the phoric and refractive changes possibly caused by visual display unit (VDU) activity. METHODS: In a longitudinal trial nearly 6000 VDU operators received two ophthalmological examinations at intervals ranging from 34 to 43 months. The findings from the two examinations were correlated to VDU work (hours daily and years of VDU work), age and sex. RESULTS: Changes in the refractive state seemed to be mainly age-related. There was a slight tendency toward hyperopia (imbalance of latent hyperopia). CONCLUSIONS: In the analysis of ocular motility, the results show no worsening capable of causing a definitive change from heterophoria to heterotropia. Heterophoric subjects, however, tend to improve both with regular office work and with additional VDU activity.