why do cats eyes glow at night?
Questions About Cats

Why Do Cat’s Eyes Glow in the Dark?

Anybody that lives with a cat will be familiar with their nocturnal nature. It’s common for a cat to be active after their owners have retired for the night. If you leave your cat indoors, you’ll often find them staring out of the window at what’s happening outside. A wandering pet’s eyes can give the impression of a pair of torches penetrating the darkness.

A cat’s eyes shine due to an additional layer behind the retina (tapetum lucidum). This layer is why cats have superior night vision to humans. The retina only reacts to bright, intense light. The tapetum lucidum is more reflective, and bounces additional light back the eye. This creates the glowing effect in cat’s eyes.

The anatomy of feline vision is fascinating, and can appear very complicated. This guide will simplify the science. We’ll explain how cats can see at night, and why a cat’s eyes are so striking.

How Do Cats See in the Dark?

This is due to the size of feline eyes, and a layer called the tapetum lucidum.

Cats have significantly larger eyes than humans. This is due to their nocturnal nature, and the fact that cats are born hunters. Larger eyes enhance peripheral vision for cats, helping them spot the movement of potential prey.

Bigger eyes also attract more light, which is why cats have superior night vision. Your cat will be no more able to see in pitch darkness than you.

If there is any light, however, they can process it much better. The average cat’s night vision is approximately six times stronger than that of a human. Even the dimmest light is enough to help a cat to see at night.

The glowing eye effect that follows is due to the tapetum lucidum. Located behind the retina, it bounces light back to the retina. The glowing eye effect is the reflection of this light.

Why Do Cat’s Eyes Glow at Night?

A cat’s initial vision works similarly to all mammals, including humans. Light enters the cat’s eye through the retina, and sends information to the brain. If the ambient surroundings are dark, however, everything changes.

The easiest point of comparison is flash photography in humans. Picture a photo taken in the dark, and the red-eye effect that accompanies such snapshots.

Mammalian eyes open wider in darkness, to let in as much light as possible. Flipping on a light switch forces pupils to contract, accommodating this new level of illumination.

The flash of a camera, however, is an extremely bright, intense and rapid light. Your pupils do not have time to contract when exposed to a camera flash.

This means that light reflects back through the wider eye, creating the red-eye effect. It’s the speed and intensity of the light that makes the difference. Shining a torch will not create a discolored effect, as the eyes have time to adjust.

cats eyes shine in the dark

Once light penetrates the retina of a feline, something similar occurs. The light sends a message to the brain, and creates a picture for your cat.

Due to the presence of the tapetum lucidum, however, cats need less light to see. Once light infiltrates the retina, it reaches the tapetum lucidum.

It then bounces back to your cat’s retina. This gives your cat’s eyes a second chance to process what they’re taking in. Their eyes then start to glow as a result of this reflection.

In brighter light, the glowing will cease, as the tapetum lucidum is no longer required.

Why Do Cat’s Eyes Glow Different Colors?

The color of your cat’s eyes will impact upon what color they glow at night.

The majority of cats have green or golden eyes. This means that their eyes will glow bright green in the dark.  Blue-eyed cats, however, will have a very different effect.

Any breed of cat could have blue eyes, depending on their genes and fur color. The following, however, will always have blue eyes:

  • Siamese
  • Ragdoll
  • Himalayan
  • Balinese
  • Turkish Angora
  • Snowshoe
  • Birman

If your cat has blue eyes, they’ll reflect red in the dark. This can be a little unnerving in the dead of night. It’s nothing to worry about, though. It’s just a quirk of the tapetum lucidum reflecting light through a filter of blue.

My Cat’s Eyes Don’t Glow in the Dark

If your cat’s eyes are not glowing in the dark, they may be having vision problems. For the eyes to glow, light must hit the tapetum lucidum. For light to reach the tapetum lucidum, light must enter the retina. If your cat has a health condition that prevents this from happening, they will struggle.

The first thing to ask yourself is just how dark a room is. A cat’s eyes will only glow in particularly gloomy conditions. We have mentioned that cats see six times better in the dark than humans. Naturally, this also means that their eyes are six times more sensitive to light than ours.

If you switch on a lamp, their eyes will automatically narrow in self-preservation. This allows less light into the retina, rendering the tapetum lucidum redundant.

If you are concerned about your cat’s eyesight, get them to a vet. Many medical conditions could restrict vision. Also, be vigilant about having your cat’s vision checked if they have white fur. Cats of this color can often be prone to early-onset blindness.

How Do I Know That My Cat’s Eyes are Healthy?

Cat’s eyes are beautiful and striking, and should stay that way. If your cat’s eyes aren’t wide, clear and devoid of discharge, it’s a bad sign.

Your cat should also have equally sized eyes, and not be squinting. A vet should also investigate any sign of redness. If your cat’s eye appears cloudy, they could have a cataract that requires investigation.

You can test your cat’s vision at home by conducting these experiments:

  • Hold your finger in front of your cat’s face, and move it from side to side. Be careful not to poke your cat in the eye! Your cat should blink, or turn their face away. This means that they have seen your hand. If they suddenly lunge, if your cat may be struggling to see your hand. They could be acting in self-defense, because they smell you but cannot see.
  • Shine a gentle torch beam toward your cat’s eye, and watch for a reaction. Don’t use a laser pointer – that light can be too intense, and cause damage. Naturally, however, few cats can resist chasing a laser pointer along the ground. This is another common test of vision.
  • Drop something light from a height above your cat’s head. If they can see appropriately, your cat will likely follow the sight due to hunting instincts. If your cat shows no interest, they may not be able to see the item.
  • Create a safe obstacle course for your cat. This will involve placing things in the path that they usually follow. While you will instinctively remember a path around the home, they’ll avoid obstacles in their sight. If your cat becomes uncharacteristically clumsy, they are struggling to see.
  • Watch how your cat jumps down from heights. A cat with normal vision will judge the distance, and make the leap. Cats that feel their way around with their paws and climb down may be going blind.

Running these basic tests does not supersede the need for professional attention. However, it will make it easier for your vet to diagnose any problems.

Medical Conditions That Impact Upon a Cat’s Eyes

The Cornell Feline Health Center lists the vision problems that impact upon cats. These include:

Cataracts

These can vary in size, and as a result, they vary in impact upon your cat. A cataract is a medical condition in which the eye clouds over.

This prevents light from reaching the retina, and thus restricts both night and day vision. Cataracts can be a side effect of health concerns such as hypertension or diabetes.

In such an instance, managing the root cause will deal with the cataract. Alternatively, they may develop with old age. If this is the case, the cataract(s) will need to be treated surgically.

Glaucoma

This can be a grave concern for cats. The condition arises when fluid builds up behind the eye, damaging optic nerves. This creates a cloudy effect, and forces the eyes to bulge and enlarge.

Some breeds of cat, particularly Siamese and Burmese cats, are more genetically predisposed to glaucoma. The condition cannot be cured, and will sadly lead to eventual blindness.

If caught early enough, however, it can be slowed down and managed.

Conjunctivitis

This is extremely common in cats. So much so, that a cat that never experiences the condition is rare. The condition involves inflammation of the conjunctiva, which lubricates the eye.

If your cat’s eye becomes irritated, they’ll be at risk of conjunctivitis. The symptoms include excessive blinking, squinting, and the release of discharge from the eye.

Conjunctivitis will often right itself over time, but it can be uncomfortable for your cat. A vet can prescribe eye drops or ointments that aid with this.

Viral and Bacterial Infections

Many bacterial or viral infections can impact upon a cat’s eyesight. Sadly, there is no cure for these conditions. Veterinary help can enhance a cat’s quality of life in the time they have left, though. This could include saving your cat’s eyesight.

why do cats eyes glow different colors?

Here are some of the viral infections that could affect your cat’s eyes:

  • Feline Immunodeficiency Virus (FIV) is akin to HIV in humans. This condition is most often passed on through bites from infected cats. It will gradually diminish your cat’s immune system. Among the problems, this will cause your cat are eye infections they would ordinarily fight off.
  • Feline Leukemia Virus (FeLV) is another infectious disease that attacks the entire body. Like FIV, this condition attacks your cat’s immunity to secondary viruses. This could lead to illnesses as serious as cancer, and it will impact your cat’s vision.
  • Feline Infectious Peritonitis (FIP) starts life as a very common condition known as Feline Coronavirus. Your cat may have experienced – or presently be living with – the latter, with no ill effects. Some unfortunate cats find that the coronavirus mutates into FIP, however. Among numerous other symptoms, FIP causes severe inflammation of the eyes.

Never sleep on any of these potential ailments in your cat. If not treated, they will have a serious impact on your pet’s vision and general health.

Do Cats Naturally Lose Their Night Vision as They Grow Older?

As cats reach their senior years, they will start to struggle with their eyesight. Night vision is not likely to fade any sooner or later than anything else. Over time, however, the less your cat sees, the more restricted their night vision will be.

Cats can still live with weak eyesight. Even a healthy cat is comparatively near-sighted, and they rely on other senses just as much. If your cat loses their vision slowly over time, they’ll barely notice when it completely fades.

This will be dangerous, though. It’s advisable to keep older pets indoors after a dark night, for their safety.

Look into your cat’s eyes next time they wake you up demanding a midnight treat. The chances are, they will be the first thing that you can see. This is perfectly normal and natural, and nothing to be afraid of. Even if they are glowing deep red, it’s just a quirk of the light.

It’s worse if your cat’s eyes don’t shine in the dark. This suggests that your cat is struggling to see. Think of your cat’s eyes as two tiny torches that illuminate the night. They may look a little spooky when you’re half-asleep, but take solace. These penetrating beams of light mean that your cat’s eyes are perfectly healthy.