why do cats eyes glow at night?
Questions About Cats

Why Do Cat’s Eyes Glow in The Dark? (Eyeshine)

Cats are often erroneously considered nocturnal due to their night vision. If you have ever watched a cat in the dark, you will notice its graceful movement. In addition, a cat’s eyes tend to glow like tiny torchlights.

This glowing effect, known as eyeshine, is a natural occurrence. When a cat widens its pupils to adjust to dim illumination, light enters the retina. It then bounces off an additional layer behind the retina, called the tapetum lucidum. This is what provides the colorful, glowing effect of the cat’s eyes. Light is reflecting from the cells behind the retina.

The color that a cat’s eyes glow at night depends on a range of factors. Common shades include green, blue, and gold. What matters most is that a cat’s eyes illuminate in gloomy conditions.

Can Cats See in the Dark?

Some people mistakenly believe that cats are nocturnal. This is because cats move with grace and ease at night, as though able to see perfectly. To an extent, this is true. Cats cannot see in complete darkness, but they do have superior night vision to humans.

This is primarily due to the shape and size of a cat’s eye. The feline eye is large and round, designed to afford excellent peripheral vision. In addition, this aids feline night vision. The large size of a cat’s eyes ensures that it absorbs and reflects even the dimmest light.

Streetlamps, or even the light of the moon, will provide a cat with enough illumination to see. This means the feline can hunt, and detect predators, by night. In addition, cats feel their way around in the dark using their whiskers.

It is impossible to miss a cat’s eyes in the dark. They glow like small but penetrative flashlights in the gloom. This may look a little eerie, but it is a good thing. It means that your cat’s night vison is operating at full capacity.

Why Cats Eyes Glow At Night

A cat’s glowing eyes could be compared to the red-eye effect of human photography. When exposed to flash photography, our eyes reflect bright light from our retina. This appears red, as the image captures reflections of the blood vessels behind the eye.

Cat eyes usually glow a different, bright color. This is due to the tapetum lucidum, a layer of reflective cells behind a cat’s retina. Tapetum lucidum translates as “shining layer” in the original Latin.

The tapetum lucidum is essentially a second chance for a cat to see. Cats’ vision revolves around light entering the eye. This light is then reflected by the retina. The tapetum lucidum absorbs any light that escaped the retina. This improves feline night vision by some 44%.

The glowing effect occurs through this reflection process. As cats have such wide eyes, plenty of light is taken in. The cells found in the tapetum lucidum then bounce this light back, creating illumination. The brighter a cat’s eyes are glowing, the stronger its vision will be.

cats eyes shine in the dark

Why Do Cat’s Eyes Glow Different Colors?

The color that cat’s eyes glow in the dark depends on a range of factors. The pigmentation of eyes and fur are prominent influences. Age will also change the color of a cat’s eyes at night. As the cat grows older, the tapetum lucidum becomes less impactful.

You may find that your cat’s eyes glow a different color to their usual shade. This is nothing to be concerned about. The illumination of a cat’s eyes is not the iris itself. It is a composition of cells found in a cat’s tapetum lucidum, which magnifies this coloring.

The most common elements found in a cat’s tapetum lucidum are zinc and riboflavin. The latter, in particular, is common the feline eye. An excess or inadequacy of these cells will influence eye color at night.

Green Eyes

Green is the most common color for feline eyes to glow in the dark. This is partly because shades of green are among the most common eye colors in cats. The following breeds of cat should always have green eyes, in light and dark conditions:

  • Abyssinian
  • Egyptian Mau
  • Havana Brown
  • Norwegian Forest Cat
  • Russian Blue
  • Sphynx
  • Turkish Angora

Even if your cat has green eyes, not all feline eyes glow the same shade. There are subtle differences in shades of green, even within identical breeds and siblings. Also be aware that alternative iris colors can still glow green at night.

This is a response to the cells found in the tapetum lucidum. A blue-eyed cat with green pupils at night is nothing to be concerned about. Glowing green eyes should be considered healthy and positive.

Blue Eyes

All kittens are born with blue eyes. This means that young cats, in particular, will display glowing blue eyes at night. Over time, the color of many cat eyes changes. Blue eyes are common in certain adult cat breeds, though. Notable examples of blue-eyed felines are:

  • Balinese
  • Birman
  • Himalayan
  • Javanese
  • Persian
  • Siamese

If your cat’s eyes are usually blue and they glow this color, it’s rarely a cause for concern. However, if you your cat has white fur and blue eyes, check for black seal-points. This suggests that the cat will retain age-appropriate levels of vision.

Unfortunately, white-furred, blue-eyed cats without these markings can be prone to early blindness. This will lead to eyes glowing red at night. The tapetum lucidum is not functioning appropriately. Regularly check the eyesight of a pure white, blue-eyed cat.

Yellow or Gold Eyes

Siamese cats have blue eyes, but their eyes frequently glow yellow. This is a natural quirk of the Siamese breed, and no cause for concern.

In other breeds, yellow eyes can be a symptom of riboflavin in the cat’s diet. Consumed to excess, this vitamin can cause liver damage. Thankfully, such toxicity is rare in felines. Cats naturally have more riboflavin in the tapetum lucidum than zinc.

If you are concerned, increase your cat’s intake of animal meats and fats. This helps the cat ingest more taurine, countering the riboflavin and boosting night vision. Overall, a deficiency of this vitamin is more harmful than an apparent excess.

Red Eyes

If your cat’s eyes glow red in the dark, it suggests the tapetum lucidum is failing. This creates the same impact as human photography, as discussed preciously. Your cat’s eyes are reflecting the muscle behind the retina. Light is not reaching the tapetum lucidum.

This is increasingly common in senior cats. Like all body parts, a cat’s eyes start to degrade with age. Check your cat’s vision and ensure it is not failing completely. Dietary changes and vitamin supplements may slow down early-onset vision loss.

Red eyes could also be a result of a surprising light source. If a cat’s eyes were not expecting to be flooded with light, they will rapidly dilate. This can lead to a bloodshot appearance. This should be a temporary one-off though, not a regular aesthetic.

Mismatched Colors

If a cat has mismatched eye colors, this perfectly natural. The tapetum lucidum is simply reflecting the varying core colors. In addition, if you only spot this issue from particular angles, do not worry. This is just a matter of light reflecting from changeable positions.

If the issue comes along suddenly, it is possible that vision is failing in one of your cat’s eyes. Cover one eye at a time and test your cat’s eyesight at home. Consider if the cat could have had eye trauma in its recent past.

If trauma is not to blame, your cat may have a cataract in one eye. These can impact feline eyes in a singular capacity. Your cat may also be overcompensating for failing vision in one eye. This will result in dilating one pupil more than the other.

Cat’s Eyes Don’t Glow in the Dark

A cat’s eyes should always glow in dim conditions. This is a sign of healthy, functioning vision. If your cat’s eyes fail to illuminate in gloomy conditions, it may be struggling to see.

A lack of bright color suggests that light is not reaching the retina. This, in turn, means that light is not reaching the tapetum lucidum. As a result of this, your cat will struggle to see in the dark. These circumstances suggest a generic vision problem. Causes of eyesight issues in felines include:

  • Glaucoma
  • Conjunctivitis
  • Cataracts in one or both eyes
  • Viral Infections (including Feline Immunodeficiency Virus, Feline Leukemia Virus or Feline Infectious Peritonitis)
  • Taurine insufficiency
  • Vitamin A insufficiency

Before you worry, check how dark a room is. The tapetum lucidum needs some light to reflect. Cat eyes are no more functional in pitch darkness than those of a human. Equally, if you switch on a light, the cat’s eyes should narrow in self-preservation. This prevents light from reaching the retina and tapetum lucidum.

You can check your cat’s vision at home. Do so during daylight hours, when your cat is awake and alert. Techniques for home eye tests include:

  • Shine a laser pointer in front of your cat and check for a reaction
  • Drop a feather (or other light, silent object) and watch if your hunts it
  • Place soft, non-dangerous objects in your cat’s path to food, water, or litter
  • Shine a dim torch into your cat’s eyes, checking to ensure the eye contracts
  • Watch your cat negotiate cat trees and stairs, ensuring it moves with confidence

If your cat does not respond to these stimuli, speak to a vet. As explained by Vision Research, temporary light blindness can be reversed. Learning the root cause of blindness is key to understanding if this is applicable.

why do cats eyes glow different colors?

My Cat’s Eyes Glow During Daylight

A cat’s eyes should only glow at night, especially for prolonged periods. If your cat’s eyes seem to glow by day, in bright light, something is amiss. This suggests that your cat’s pupils are unnecessarily dilated, attracting more light than is required.

This will be uncomfortable for your cat. No feline will willfully open its eyes wide in broad daylight. Quite the opposite – when faced with a direct light source, cats narrow their eyes. Explanations for this phenomenon include:

  • Consumption of toxins
  • Stress and anxiety
  • Hypertension (high blood pressure)
  • Key-Gaskell Syndrome
  • Diminishing eyesight

Occasional eyeshine during daylight is not a concern. Your cat could have widened its eyes in fascination. Potential prey may have been spotted in the cat’s peripheral vision, for example. If the cat’s eyes permanently glow by day, veterinary help is recommended.

A cat’s eyes glowing in the dark is not spooky or sinister. It’s all part of functional feline eyesight. Take solace if your cat’s eyes act as organic flashlights in the night. It means you have a happy and healthy cat.