You eagerly sift through your newly developed photos, anticipating the award-winning photos of your adorable, brown-eyed dog. Instead, ghostly green eyes shine back at you, as if your romping, happy puppy
had lost his soul.
Why does your dog's eyes shine in such a creepy way in photos? The answer is, for the same reasons our
eyes come out red – because of the way the flash is reflected off the back of our eyes. The difference in color of the reflection is due to the structure of the eye. In a person, flash photography makes our eyes appear devilish red. This is because the flash reflects off the a blood vessel rich layer behind the retina.
In dogs (and many other animals), the retina has a reflective layer behind it called the tapetum lucidum. This layer acts like a mirror, reflecting light at the back of their eyes. The reflective layer is what helps dogs and cats see better at night. Light is reflected outward, giving the dog's retina a second chance to absorb to absorb the rays .
Light that is not absorbed exits the eye, appearing as the "eyeshine" seen in photos, from headlights, flashlights, etc. This ability comes at a price, as dogs cannot see detail as well as humans (they are more attuned to seeing motion).
Note: Some dogs lack pigment in their tapetum lucidum. In these individuals their "eyeshine" is red, as it is in humans.