Eyeshine In The Night

A three-month-old black Labrador puppy with apparent eye shine

Eyeshine is a visible effect of the tapetum lucidum. When light shines into the eye of an animal having a tapetum lucidum, the pupil appears to glow. Eyeshine can be seen in many animals, in nature and in flash photographs. In low light, a hand-held flashlight is sufficient to produce eyeshine that is highly visible to humans (despite our inferior night vision); this technique, spotlighting, is used by naturalists and hunters to search for animals at night. Eyeshine occurs in a wide variety of colors including white, blue, green,yellow, pink and red. However, since eyeshine leads to iridescence, the color varies slightly with the angle at which it is seen and the minerals which make up the reflective tapetum-lucidum crystals

White eyeshine occurs in many fish, especially walleye; blue eyeshine occurs in many mammals such as horses; green eyeshine occurs in mammals such as cats,dogs, and raccoons; and red eyeshine occurs in coyote, rodents, opossums and birds.^{[citation needed]}

Despite it being present in some primates, the human eye has no tapetum lucidum, hence no eyeshine. However, in humans and animals two effects can occur that may resemble eyeshine: leukocoria (white shine, indicative of abnormalities includingcataracts, cancers, and other problems) and red-eye effect.