Our cats are endlessly unique and curious creatures with a whole host of qualities that make them special. One of these qualities is the manner in which their eyes reflect light in the dark – a fierce forest green that may startle you from across the bedroom when you wake up to check your phone at night. But why do cats‘ eyes glow? And which other animals possess this unique talent?
Glowing cat eyes are the result of a unique structure that reflects light back out of the eye. Your cat, like many other predators, uses this adaptation to navigate through a darker world. Ready to find out more about your cat’s eyeshine? Shut off the lights, settle down with your furry friend, and read on with us.
Why Do Cat Eyes Glow in the Dark?
Your cat’s eyes feature a unique layer of tissue known as the tapetum lucidum. This layer lies behind the retina and acts as a reflector. It reflects visible light back through the retina to increase the light available to the eye’s photoreceptors, making your cat’s night vision much more honed than ours. In cats, the tapetum lucidum increases their visual sensitivity by around 44%, allowing them to see the light that we cannot. This is important to cats because they are crepuscular (dawn and dusk) predators, and as such, they need to navigate the world in darker conditions to survive.
With this in mind, you may now wonder why your cat’s eyes reflect a specific color. The tapetum lucidum is an iridescent structure – in cats, tigers, and dogs, you will find that it reflects a green color against a camera flash. However, the color will vary depending on the angle at which you are viewing it. Interestingly, cats with blue eyes may display both an eyeshine and red-eye effect when photographed with a flash. This means that the eyes may glow a bright red when captured in the dark!
Do Other Animals’ Eyes Glow Too?
Many species that need to be able to see at night have a tapetum lucidum, similar to your own cat. This includes both predators and prey alike. However, there are several different types of tapetum spread between different groups. For example, teleost (bony) fish, crocodilians, marsupials, and fruit bats have the retinal tapetum. Cartilaginous fish (e.g. sharks, rays, and sawfish) possess a choroidal guanine tapetum. Your cat, as well as rodents, cetacea (e.g. whales, dolphins, and porpoises), and many carnivores possess a choroidal tapetum cellulosum. Lastly, the choroidal tapetum fibrosum is usually in cows, sheep, goats, and horses. While the structures of each are different, all types of tapetum lucidum act to increase the animal’s light sensitivity in dark conditions. This is also why certain species’ eyes glow specific colors when light is shone at them in the dark.
Should I Worry If My Cat’s Eyes Glow?
There is no need for concern if you notice your cat’s eyes reflecting light in the dark. This is a perfectly natural phenomenon for all pet cats. Conversely, your concern should be raised if your cat’s eyes do not reflect light back at you at night when you use a camera flash. This indicates a problem with their vision, and a trip to the vet is highly advised. Common ocular conditions in cats include conjunctivitis, eye ulcers, cataracts, retinal detachment, uveitis, masses and tumors, lens luxation, and glaucoma. Each of these conditions may interfere with light reflecting back out of the eye, thereby reducing or completely stopping the “glowing eyes” effect at night. These conditions can be painful, and uncomfortable, or result in a total loss of vision for your cat without veterinary intervention as soon as possible.
Why Do Cats Eyes Glow: FAQs
Still wondering why cats’ eyes glow in the dark? Feel free to check out our Frequently Asked Questions for more details. If in doubt about your cat’s eye health, always contact your local vet for advice.
When your cat’s eyes glow in the dark, it means that a layer of tissue behind its retina is reflecting visible light back out of the eye. By doing this, your cat’s eyes direct light back to the photoreceptors in their eyes. This increases their night vision and allows them to perceive the light that we cannot see. However, for this visible “eyeshine” effect to occur, your cat’s eyes need at least a little light. This is why it’s most commonly noticed when shining a torch or camera flash toward a cat in the dark.
If you notice that only one of your cat’s eyes reflects light in the dark, it suggests that there is something interfering with their eyesight, and a trip to the vet is highly advised. When your cat’s eyes fail to reflect light from a torch or camera flash at night, your cat may be struggling with any number of ocular conditions, including cataracts, glaucoma, eye ulcers, or lens luxation. In any case, it’s essential to get your furry friend veterinary assistance as soon as possible. Untreated ocular conditions can be painful or lead to total loss of vision.
Many diurnal animals, including us humans, lack a tapetum lucidum because we do not “need” to be able to see in the dark. Such other species include haplorhine primates (e.g. marmosets, tamarins, spider monkeys, gibbons, and great apes), squirrels, red kangaroos, and pigs. However, humans may exhibit a weak reflection from the fundus, as seen with the red-eye effect associated with flash photography.
In most cases, a cat’s eyes will reflect a green color back at you when you shine a light on them. However, the color that they reflect often depends on a range of factors. These include the angle of the light and the color of your cat’s eyes. So, you may find that your cat’s eyes reflect a golden yellow from time to time, as well as red, green, or blue. All of these colors are normal for cats!
Like humans, cats cannot see in total darkness. However, they do have superior vision than us in low light conditions. Your cat’s tapetum lucidum works by reflecting light back out of the eye, directing it to the photoreceptors, which allows them to make better use of the small amounts of light. Thanks to your cat’s tapetum lucidum, their sensitivity to light are around six times greater than your own!
Glowing cat eyes are all thanks to your furry friend’s unique eye structure. If in doubt about your cat’s ocular health, always speak to your local vet.