What is "tapetum lucidum"

n. A layer of tissue in the eye of many vertebrate animals, immediately behind or sometimes within the retina, that reflects visible light so as to increase the light available to the photoreceptors.

The tapetum lucidum ( Latin: "bright tapestry; coverlet", plural tapeta lucida) is a layer of tissue in the eye of many vertebrates. Lying immediately behind the retina, it reflects visible light back through the retina, increasing the light available to the photoreceptors, though blurring the initial image of the light on focus. 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.

Similar adaptations occur in some species of spiders, although these are not the result of a tapetum lucidum . Most primates, including humans, lack a tapetum lucidum, and compensate for this by perceptive recognition methods.