Wednesday, June 27, 2007

Canine Eye Color Reflections

Willy with her *Stop and Go* eyes

Our shepherd / husky mix dog, Willy, has brown eyes that reflect two different colors. I had never noticed this in another dog, but it probably is at least as common as a dog having two differently colored eyes.

The green reflection, like you see in a cat's eyes at night, is caused by the tapetum lucidum layer on the canine (or feline) retina. That layer is thought to cause a double reflection of light to the back of the eye, which increases the canine night vision (http://www.vet.upenn.edu/schoolresources/communications/publications/bellwether/52/canine_symposium.html).

Obviously, then, Willy lacks the tapetum layer on her right eye since only her left eye reflects green. Our Siberian Husky, Lobo, had red reflections from both of his eyes. We've never specifically tested the dogs, but from the reading I've done, Lobo's night vision is probably not as good as Willy's - even though Willy has just one eye with the tapetum layer.