Ergonomic aspects of the health and safety of VDT work in Japan: a review.

Many ficld surveys and medical check-ups suggest that the visual load of VDT work is heavy, and that complaints and subsequent medical diagnoses rclatc to the user of VDTs. However, very few surveys were epidemiologically wcll designed. Some clinical cases were diagnosed as relating to VDT work; however, the pathogeny was not disclosed. The most commonly mcasurcd and examined physiological response to evaluate objectively the load and fatigue in VDT work was visual accommodation. There are other indices, such as eye movement, pupil size, critical flicker frequency, ocular tension, tears, surface temperature of cornea, electroencephalogram, but they lack consistency and strength in their relation with VDT work. There is no index that can help to evaluate the load and fatigue caused by VDT work alone. There arc also few physiological indices which are compatible with the subjective symptoms often observed in VDT work. Many studies show that the workload is greater in VDT work than in paper work. Many experimental evaluations of the photometric characteristics of' VDT screens support the contention that positive presentation (bright characters on a dark background) is better than the negative presentation (dark characters on a light background). 0 With regard to environmental factors, there are some experimental studies on the effect of static electricity or magnetic field on eyesight. In comparison with VDT work in Europe and America, some experimental studies show that VDT work in Japan additionally increases visual load because of text processing of Japanese characters. Some experimental studies aim to obtain evidence to establish rules regulating continuously working minutes or daily working hours spent on VDT work. However, lhese are not so systematic and extensive. 0 It is suggested that astigmatism increases visual load as well as presbyopia. There is no special legislation regulating VDT work in Japan.