Why Do Dogs' Eyes Glow at Night?

Dogs' eyes glow because they have a mirror-like layer at the back of the eye called the tapetum lucidum. Light that passes through the retina without being caught bounces off this layer and goes back through the retina a second time. That gives the light-sensing cells a second chance, which helps dogs see better in dim light. The light that bounces back out of the eye is the glow you see in a flash photo or headlights. It is often green, yellow or blue.

The main parts of a dog's eye are: the cornea (the clear front window), the sclera (the white outer wall), the iris (the colored ring that controls how much light gets in), the pupil (the opening in the iris), the lens (focuses light), the retina (the light-sensing layer at the back with rods for dim light and cones for color), the tapetum lucidum (the reflective layer), and the optic nerve, which carries signals to the brain.

Dogs also have eyelids, a third eyelid (a protective membrane in the inner corner), and tear glands. Compared with people, dogs have many more rods, fewer cones and see fewer colors, mainly blues and yellows.

Our page on dog eye anatomy and how dogs see has more detail and would be a good source for your project.

This is general information, not a diagnosis. Please follow your own vet's advice.