Dark adaptation

Dark adaptation is a process by which the eye adjusts to low levels of light after exposure to high levels of light. This process involves the retina of the eye, specifically the rod cells and cone cells, which are responsible for vision in low light and color vision, respectively.

Process

The process of dark adaptation begins when the eye is exposed to a sudden decrease in light. The rod cells and cone cells in the retina undergo a series of chemical reactions to increase their sensitivity to light. This process takes approximately 20 to 30 minutes for the rod cells and 5 to 7 minutes for the cone cells.

The first stage of dark adaptation involves the bleaching of the photopigment in the rod cells and cone cells. This is followed by the regeneration of the photopigment, which increases the sensitivity of the cells to light.

The final stage of dark adaptation is the adjustment of the pupil to allow more light to enter the eye. This is controlled by the iris, which contracts or expands to control the amount of light entering the eye.

Factors affecting dark adaptation

Several factors can affect the process of dark adaptation. These include the initial level of light exposure, the duration of light exposure, and the individual's age and overall health. Certain medical conditions, such as vitamin A deficiency and retinitis pigmentosa, can also affect dark adaptation.

Clinical significance

Dark adaptation tests are used in ophthalmology to diagnose and monitor certain eye conditions. These tests measure the time it takes for the eye to adapt to darkness and can help identify problems with the rod cells and cone cells.

See also

• Light adaptation
• Night vision
• Photoreceptor cell
• Visual perception

References

Dark adaptation Resources
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