Visual Light- and Dark-Adaptation

The human visual system works effectively over an enormous range of light intensities from starlight to bright sunlight. This is made possible by adjustments of its operating level to match the ambient illumination: Light adaptation is an adjustment to higher levels of illumination, and dark adaptation is an adjustment to lower levels. This entry covers the processes that mediate adaptation, adaptation and visual processing, scotopic recovery processes, color, anomalies of dark adaptation, light adaptation, and electrophysiology.

Processes That Mediate Adaptation

The pupil opens wide at night and thereby lets in up to 10 times more light, but this is only a small part of the entire adaptive range. (This effect is greater in species with slit pupils.) Adaptation in humans is instead controlled primarily within the eye, ...

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