Why Do Cats’ Eyes Glow?

Cat eyes glowing in the dark

Do cats really capture and hold sunlight in their eyes to serve as a light source during the night or is there a scientific explanation for these felines’ glowing eyes?

The Ancient Egyptians Revered Cats

Ancient Egyptians believed that cats are magical creatures. The felines were so special that killing one was even considered a crime punishable by death. Indeed, cats ruled in ancient Egypt and part of the reason for that is that the ancients believed that they have the supernatural power to harness the sunlight in their eyes. So special were these felines back in the day that they were even worshipped as gods.

However, the cats’ glowing eyes have nothing to do with any supernatural power as the ancients believed. There is either a scientific or medical explanation for why their eyes shine depending on whether it glows during the day or night. Let’s find out why cats’ eyes glow and whether or not it should cause serious concern for cat owners.

Why do cats’ eyes glow?

Cats’ eyes glow in the dark because of the phenomenon called tapetum lucidum.

Tapetum lucidum is a phenomenon that typically occurs among vertebrates and other animals, especially the ones that are considered nocturnal. In Latin, ‘tapetum lucidum‘ means ‘shiny layer’ and refers to a special layer of tissue at the back of your feline’s retina. This tissue serves as a reflector that aids in increasing the light of your pet’s visual system and enhancing its ability to see in the dark.

With their tapetum lucidum, your cat is equipped with superior night vision enough for it to survive the dangers that could be possibly lurking in the darkness. Contrary to what the ancients believed, cats do not have the supernatural power to capture sunlight but only the ability to reflect the light that’s already present in their surroundings. When caught in lights during the night, their eyes would make an eerie glow in order to adjust to their dark environment.

Cats’ eyes glowing during the daytime is a possible sign that there might be a problem with their vision

While it is normal for cats’ eyes to glow during the night, it is not normal for their eyes to glow during the day. If your cat’s eyes glow during the daytime, then it means that its pupils are dilated. When their eyes reflect light at high levels, their pupils become dilated which should not happen during the day. As a cat owner, seeing your pet’s eyes glowing during the day requires investigation as it may be afraid, hurt, or may be suffering from an eye condition that should be checked by the veterinarian.

To significantly boost the cats’ vision as they guard their territory or hunt at night

Just like the long necks of giraffes, the wing colors of the peppered moths, or the white furs of the arctic animals, cats also have their tapetum lucidum which can be attributed to natural selection. It is a heritable trait necessary to increase the chances of the feline’s survival. With their glowing eyes, they can significantly boost their vision to aid them while guarding their home range or hunting at night.

Although this mechanism of natural selection would most benefit the felines in the wild, it can not be denied that the cats’ glowing eyes are useful for domesticated felines as well. As they can see better in the dark compared to their human counterparts, they will be able to watch discreetly if there are any intruders and discourage any unwanted visitors from entering their homes. So, if you notice a cat with glowing eyes staring at you while you’re out in the dark, then know that the feline is only trying to keep its territory safe.

Why do cats’ eyes glow in varying colors?

The tapetum lucidum in cats reflects a light that can appear to be yellow, green, or blue. Since cats do not all have the same amount of zinc or riboflavin in their eyes, you will notice that not all cats share the same eye shine color. Younger cats have a pretty blue eye shine but know that this glow would likely change in color as the feline gets older. Also, the eyes of younger cats tend to glow brighter because of their young tapetum lucidum. As the cat grows older, its tapetum lucidum will be less powerful and the glow in its eyes will get dimmer. When it comes to adult cats, their eye shine may appear in yellow or green color.

It’s been a long time since I saw my cat’s eyes glow in the dark, is it normal?

It is not normal for a cat’s eye to be non-reflective during the night as this is a heritable trait common to all felines. Your cat needs its eye shine as it effectively aids the pet in navigating the world around them at night and not being able to make its eyes glow could indicate a health issue that should be checked by the veterinarian.

Eye problems such as cataracts, glaucoma, conjunctivitis, or other eye infection can hinder the tapetum lucidum to function properly, thus, preventing their eyes from glowing.

Can my lights at home cause harm to my cat’s eyes?

The tapetum lucidum provides your cat’s ability to reflect light which aids them in low-light environments. With that being said, it is only normal for cat owners to start looking at the lighting fixtures in the home to ensure that they’re providing a safe environment for their pets. That is actually a valid concern because although cats reflect lights only when necessary, there are still some types of lighting that can cause harm to their eyes.

Avoid blue and violet lights as much as possible as they can penetrate deeply into your pet’s eyes and potentially lead them to develop cataracts or any other eye condition. Also, prolonged exposure to light bulbs can irritate your cat’s eyes, so it’s better to avoid them as well. When it comes to home lighting, LED lights are deemed safer for your cat as they will not cause any damage to its eyes but make sure that you have the light fixed right away once it starts flickering.

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