Animals eyes do not glow, their eyes only reflect light.
This reflection of light, which appears to make the animal's eye
glow, is called eyeshine and it is caused by the tapetum lucidum,
which is a layer of tissue in the eyes of many vertebrate animals.
The tapetum lucidum allows the animal to see better in low-light
situations (such as after dark) by reflecting the light back into
the retina. When a photo is taken of an animal that has tapetum
lucidum in it's eyes, the light reflected from the flash of the
photo often makes the eyes appear to glow. The same thing occurs
when light is flashed into the eyes of animals that contain tapetum
lucidum after dark.
