Dateline: 01/31/00
Have you ever seen the glow of an animal's eyes reflecting the headlights on a car or
the flashlight you are holding? If not, you can try it. You will need:
Take the animal and the flashlight into a darkened room. It does not have to be
totally dark, but the dimmer the light is, the better. Place your pet on one side of
the room and move to the other side. This may be easier with some pets than
others. Hold the flashlight beside your head, near your eyes and shine it towards
your pet. You will see the animal's eyes glowing.
Why do its eyes glow? It is because of something called a tapetum lucidum.
This is a shiny layer, behind the light sensitive cells in the eye. When light
enters the animal's eye, it passes over the light sensitive cells, hits the shiny surface
of the tapetum lucidum and reflects back over the cells a second time. Each cell
gets twice as much stimulation, allowing the animal to see in much dimmer light.
Interestingly, different animals have different color eye shine.Cats and dogs usually have
green eye shine. So do deer. Alligators have red eye shine. Opossums eyes
shine pink. In spite of the red eyes that show up in photos, humans do not have a
tapetum lucidum and do not have eye shine. According to my references, neither do
monkeys or birds. This eperiment was re-printed with permission from Robert Krampf
Previous Articles