Division on Visual Impairments

DVI Quarterly Winter 2012 (Volume 57, Number 2)

A quarterly newsletter from the Council for Exceptional Children's Division on Visual Impairments containing practitioner tips for Teachers of Students with Visual Impairments, Certified Orientation and Mobility Specialists, and other professionals.

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Winter 2012 wavelength of light which strikes it. Each unit of work done by a single photoreceptor generates one unit of cellular waste product, which must be carried away by the eye's natural system of waste disposal. In the diseased or injured eye, the natural system of waste disposal is often compromised. Thus, while the retinal cells are working hard to process light information, they often produce more waste product than the eye's disposal system can handle. Waste products build up in the eye and are perceived by the brain as "glare." Glare is often characterized as "fog, whiteness, blackness, or an irritating feeling." There is also "disability glare" which is glare that is so intense that it impairs a person from doing his/her daily activities. Whatever kind of glare it is, it's unpleasant to the person who experiences it. For the person who has diseased or injured eyes, it is more than unpleasant; it can be extremely painful, and it can last a very long time after the source of light is removed. How does cool white light, or light with an = 54 CONTENTS output in the predominantly blue portion of the spectrum exacerbate glare? It is simple mathematics. For every peak in a lightwave that strikes a photoreceptor, the cell does one unit of work. UV and light in the blue part of the spectrum

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