Improper lighting as an occupational hazard

The assessment of lighting conditions at work must include not only the light intensity but also other characteristics, such as shadows, contrasts and colour. The desirable quantity of light depends on the fineness of the detail and the accuracy required in performance of the task. With regard to the quality of light, many complex factors are involved such as glare, diffusion of light, direction, uniformity and distribution. Dim light associated with high visual demands may lead to eye strain and fatigue. Exposure to the dim light of inadequate illuminated work-places or to the partial darkness of a mine or a darkroom for eight hours a day over a long time, can cause both acute and chronic effects on health. Dim work-places cause headache, eye pain, lachrymation and congestion around the cornea, particularly associated with eye strain from trying to see small objects. Dark work-places cause miner's nystagmus. Distraction from visual tasks and loss of concentration may result from direct glare. This kind of glare is also associated with discomfort, annoyance, and visual fatigue. Intense direct glare may also result in temporary loss of visual ability, as in the case of drivers exposed to direct intense light from on-coming cars at night. Other kinds of glare include the indirect glare from an intense light spot which may cause blurring of vision. Reflected glare from shiny surfaces or dials can obscure details and prevent perception of visual displays. In the occupational environment, intense colours may result in fatigue of certain retinal cones.