The eyes of many animals, including cats, some dogs, shine at night. So what’s the science behind this situation? Species with glowing eyes had an eye structure that could see better in dim light. Because they either look for food or do most of their hunting at dawn and dusk.
WHY DO CAT’S EYES SHINE IN THE DARK?
All eyes reflect light, but some eyes have a special reflective structure called the ‘tapetum lucidum’ that creates a glowing appearance at night. A cat’s tapetum lucidum consists of cells with crystals that reflect light back to the retina like a mirror. This gives the retina a second chance to absorb more light.
The tapetum lucidum (Latin for “shining layer”) is actually a small mirror located behind the pupils of many nocturnal animals. It basically helps these animals see better at night. It also causes the glowing eye phenomenon known as “eye glare”.
Some of the light passes through or around the retina and hits the tapetum lucidum. The tapetum lucidum reflects visible light back from the retina, increasing the light available to photoreceptors. This allows cats to see better in the dark than humans.
Some of the light reflected from the tapetum lucidum is reflected back from the cat’s eyes. This reflected light, or eye glare, is what we see when a cat’s eyes appear to glow in the dark.
Human eyes do not have this tapetum lucidum layer.
IT IS ALSO IN SOME OTHER ANIMALS
“Many other animals that need to see at night have tapetum lucidum. This includes predators—everything from foxes to farm sheep and goats. Tapetum lucidum is also useful for fish, dolphins, and other aquatic animals because it does better in turbid, dark water,” says The Conversation. In land animals, the tapetum is located in the upper half of the eye behind the retina because they need to see the ground best, whereas in aquatic animals the tapetum covers most of the eye because they need to see around in the dark.
Although many animals have glare, some small pet dogs do not. “Most animals with blue eyes and white or light-coloured fur have also lost this trait.”
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