Postural and visual loads at VDT workplaces. II. Lighting conditions and visual impairments.

Four groups of office tasks were studied: data entry terminals, conversational terminals, traditional office work and typing. Eye impairments were observed in every group of office employees but the impairments were more frequent in VDT operators. The impairments persisted during leisure time. Vision screening tests showed the same incidence of functional eye impairments in office tasks with and without VDTs. High luminance contrasts between screen, source document and the surrounding space were associated with an increase in eye troubles. Increased oscillating luminance of screen characters was associated with lower visual acuity, and with a higher incidence of subjective and objective symptoms of eye irritation including more frequent use of eye drops. The degree of luminance oscillation of characters must be considered as an important factor in eye strain at VDT workplaces. Employees with eye defects (glasses, lowered visual acuity, uncorrected eye defects) had in general a somewhat higher incidence of...