Eyeshine

Eyeshine is a phenomenon in which the retina of certain animals' eyes appears to glow when illuminated by light. This is due to a layer of tissue in the eye called the tapetum lucidum, which reflects light back through the retina, increasing the light available to the photoreceptors and improving vision in low-light conditions.

Causes

Eyeshine is caused by the tapetum lucidum, a layer of tissue in the eye that lies immediately behind or sometimes within the retina. This tissue reflects visible light back through the retina, increasing the light available to the photoreceptors. The tapetum lucidum contributes to the superior night vision of some animals. Many of these animals are nocturnal, especially carnivores that hunt their prey at night, while others are deep sea animals.

Variations

The color of the eyeshine varies from species to species. In general, white eyeshine is produced by animals such as dogs, cats, and raccoons; green eyeshine by animals such as rodents, opossums, and birds; and red eyeshine by animals such as fish, reptiles, and amphibians.

In Humans

Humans do not have a tapetum lucidum, and thus do not experience eyeshine. However, in photography, humans can exhibit a phenomenon similar to eyeshine, known as red-eye effect, which occurs when light from a flash reflects off the blood vessels in the back of the eye.

See Also

• Tapetum lucidum
• Red-eye effect
• Night vision
• Photoreceptor cell

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