Q: Why do cats’ eyes glow in...

Q: Why do cats’ eyes glow in the dark?

A: A cat’s eye contains a special light-conserving mechanism behind the retina called the tapetum lucidum, which reflects any unabsorbed light back through the retina. The retina thus has a second chance to absorb the light, thereby increasing the animal’s ability to see under conditions of low light.

In dim light, we can often see the light reflected from the mirror-like tapetum. The color of the glow is usually greenish or golden, but the eyes of the Siamese cat reflect a brilliant ruby red.