Human Factors Issues of Glare :: Optometry Vision Glare Essays

Human Factors Issues of Glare The problem of glare affects all individuals. Although it is usually only a fleeting annoyance, glare can have grave consequences. For instance, problems caused by glare from computer screens account for 10 million optometrist examinations per year (Berman, 1998). There are two types of glare: discomfort glare and disability glare. The types of glare are distinguished by their origin. Discomfort glare comes from an external source; it is the physical sensation one experiences in the presence of a light source that is too bright. An example of discomfort glare is the experience of stepping outside on a bright day just after leaving a dark movie theater. Surfaces such as snow and sidewalks can cause discomfort glare (Ludt, 1997). Discomfort glare affects everyone. Disability glare, however, has an internal source. It is intrinsic to the individual due to aging or disease. Disability glare refers to intraocular scattering of light that interferes with normal visual functioning by decrea sing image contrast on the retina. These individuals have a debilitating sensitivity to high levels of illumination. Streetlamps, floodlights, and the sun are examples of everyday encounters that can induce, and require recovery time from, disability glare. The pervasive and insidious nature of glare demands additional research. This paper examines discomfort glare, disability glare, the reasons why they warrant further research, and the direction of this research. Because discomfort glare refers to reflection sources in the field of vision, the most simple way to guard against discomfort glare is to modify the environment. Some of the sources of discomfort glare are the sun, unshielded streetlamps, floodlights, computer screens, and parabolic luminaires. When the sun is low on the horizon, early in the morning and at dusk, discomfort glare peaks because the sunà ­s illumination is much brighter than other objects and these objects become difficult to see. (Ludt, 1997). Protective gear may be sufficient to counteract the overhead rays of the sun in between dusk and dawn. A remedy for discomfort glare caused by the sun is simply to wear a visor while outdoors. A brim that extends 3 inches forward should block light from entering the pupil. Sunglasses with yellow, orange, or red tinted lenses may decrease discomfort glare (Ludt, 1997). Unshielded streetlamps, or semi-cutoff luminaires, fail to make streets safer because their high-wattage bulbs shine light throughout the entire surrounding area. Full cutoff optics are a less bright and ultimately safer alternative.