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The dark blue, teal, and gold tapetum lucidum from the eye of a cow Retina of a mongrel dog with strong tapetal reflex. The tapetum lucidum (Latin for 'bright tapestry, coverlet'; / t ə ˈ p iː t əm ˈ l uː s ɪ d əm / tə-PEE-təm LOO-sih-dəm; pl.: tapeta lucida) [1] is a layer of tissue in the eye of many vertebrates and some other animals.
The tapetum lucidum, in animals that have it, can produce eyeshine, for example as seen in cat eyes at night. Red-eye effect, a reflection of red blood vessels, appears in the eyes of humans and other animals that have no tapetum lucidum, hence no eyeshine, and rarely in animals that have a tapetum lucidum. The red-eye effect is a photographic ...
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Choroid dissected from a calf's eye, showing black RPE and iridescent blue tapetum lucidum. The RPE was known in the 18th and 19th centuries as the pigmentum nigrum, referring to the observation that the RPE is dark (black in many animals, brown in humans); and as the tapetum nigrum, referring to the observation that in animals with a tapetum lucidum, in the region of the tapetum lucidum the ...
In some animals, the retina contains a reflective layer (the tapetum lucidum) which increases the amount of light each photosensitive cell perceives, reflecting the light out of the eye, allowing the animal to see better under low light conditions.
The tapetum lucidum reflects light back onto the retina, allowing for greater absorption in dark conditions. The iris lies between the cornea and the lens , and not only gives the eye its color, ( see "eye color," below ) but also allows varying amounts of light to pass through its center hole, the pupil .
Reflectors made of alternating layers of flat guanine crystals (refractive index, n = 1.83) and cytoplasm (n ≈ 1.33) have evolved independently in fish scales and in the tapeta of the eyes of elasmobranchs (Gur 2017). The tapetum of the bush-baby, Galago crassicaudatus, has a similar structure, but with crystals of riboflavin (n = 1.73).
Because the function of the eye is to form an image on the retina, an eye focused on a distant object has a focal surface that approximately follows the reflective tapetum lucidum structure, [citation needed] which is the condition required to form a good retroreflection.