Blue-eyed cats and dogs

Blue-eyed cats and dogs

Odd-eyed cat with eyeshine, plus red-eye effect in one eye

Heterochromatic dog with red-eye effect in blue eye

Cats and dogs with blue eyes (see Eye color) may display both eyeshine and red-eye effect. Both species have a tapetum lucidum, so their pupils may display eyeshine. In flash color photographs, however, individuals with blue eyes may also display a distinctive red eyeshine. Individuals with heterochromia may display red eyeshine in the blue eye and "normal" yellow / green / blue / white eyeshine in the other eye. These include odd-eyed cats and bi-eyed dogs. The red-eye effect is independent of the eyeshine: in some photographs of individuals with a tapetum lucidum and heterochromia, the eyeshine is dim yet the pupil of the blue eye still appears red. This is most apparent when the individual is not looking into the camera, because the tapetum lucidum is far less extensive than the retina. Eyeglow, which is sometimes seen from cats and dogs, is a result of light bouncing of the tapetum. Animals’ eyes glow as a result. Though eyeshine might seem insalubrious to the animal, it is really only a result of light bouncing off the tapetum.