"There are two kinds of light - the glow that illumines
and the glare that obscures."
- James Thurber
Impaired Light / Dark Adaptation
Homonymous hemianopsia patients frequently demonstrate problems with light and/or dark adaptation. Following acquired brain injuries, patients may suffer from several types of light and/or dark adaptation problems. Zihl and Kerkhoff reported on a study in 1990 that in a group of 90 brain injury cases, 26% showed impaired light adaptation, 23% had impaired dark adaptation and 46% showed both light and dark adaptation problems.
Light Adaptation Problems: Patients with light adaptation problems feel overwhelmed by light. They may report a “white-out” blinding glare on exposure to bright surfaces. These patients may benefit from filters to control glare and control of lighting in the environment.
Dark Adaptation Problems: These patients report that their vision is too dim. It may be so dim as to impair their functioning. Increasing lighting may be helpful.
Mixed Dark and Light Adaptation Problems: These patients usually report problems with too much light and possible “white-out blinding glare”, but when light is reduced to a comfortable level, it may be too dim to allow easy reading. The use of filter and light control are advised, but must be carefully customized to each patient.
Other Factors Effecting Light / Dark Adaptation: Many acquired brain patients may also be placed on medication that can reduce their dark adaptation. Brain injuries may also result in pupil dilation of one or both eyes, which can increase photophobia.
The Importance of the Clinical History: In taking a careful patient history, we can identify these problems and allow for improvement with filters or light modifications. Most importantly, we can educate the patient about these problems and help them understand the problem and better control their environment.
Recommended Resources
Zhil,J. & Kerkhoff, G.(1990) Foveal photopic and scotopic adaptation in patients brain damage. Clinical Vision Sciences, 5 185-195
Please contact us if you have any questions.
The Low Vision Centers of Indiana
Richard L. Windsor, O.D., F.A.A.O., D.P.N.A.P.
Craig A. Ford, O.D., F.A.A.O.
Laura K. Windsor, O.D., F.A.A.O.
Ali E. Prible, O.D.
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