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How does the human eye adjust to dark environments?
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human eye
A horizontal cross section of the human eye, showing the major parts of the eye, including the protective covering of the cornea over the front of the eye.
The human eye adjusts to dark environments through a process called dark adaptation. This involves several mechanisms:
- Pupil Dilation: The iris controls the size of the pupil, which widens in dim light to allow more light to enter the eye.1
- Rhodopsin Regeneration: In low light, the concentration of rhodopsin, a light-sensitive pigment in the rod cells of the retina, increases. Rhodopsin is crucial for vision in dim conditions.23
- Increased Rod Sensitivity: Rod cells are highly sensitive to light and are responsible for night vision. As rhodopsin regenerates, rods become more sensitive, enabling vision in near darkness.24
This adaptation allows the eye to function effectively across a wide range of light intensities.4