What Is Light & Dark Adaptation of the Eye?
The effects of light and dark adaptation can be easily observed at the movie theater: When you move from a well-lit lobby into the dark movie theater, it is normal to have some difficulty navigating the movie theater until your eyes have adapted to the dark, or "dark-adapted."
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Process of Dark Adaptation
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The American Optometric Association reports that dark adaptation occurs as a result of changes that happen at the cellular level in the retina. When a person is in a dark room, the rods and cones undergo a chemical change that allows the eyes to become more sensitive to light than if they were in a well-lit room.
Time for Dark Adaptation to Occur
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Dark adaptation occurs very slowly. The cone cells can fully dark adapt in a matter of minutes. However, they do not function as well in the dark as the rods do. According to the American Optometric Association, under normal circumstances, it takes 30 to 45 minutes for the rods to fully dark-adapt.
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Process of Light Adaptation
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Light adaptation occurs in the same fashion as dark adaptation, but it involves the eyes reducing their sensitivity to light.
Time for Light Adaptation to Occur
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Light adaptation happens in a matter of a few minutes. This is because the cones are responsible for vision in well-lit areas, and they adapt more quickly.
How to Measure Light and Dark Adaptation
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Light and dark adaptation can be measured using an electro-diagnostic instrument known as an electro-oculogram. The electro-oculogram is a complicated test, and it is rarely used in eye care.
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References
Resources
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