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Why Is My Cat Squinting One Eye? (Vet Answer)

Written by: Dr. Joanna Woodnutt BVM BVS (Veterinarian)

Last Updated on July 10, 2024 by Catster Editorial Team

cat with eye discharge

Why Is My Cat Squinting One Eye? (Vet Answer)


Dr. Joanna Woodnutt Photo


Dr. Joanna Woodnutt

MRCVS, Veterinarian

The information is current and up-to-date in accordance with the latest veterinarian research.

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Our cats squint at us for several reasons. It can be a gesture of affection, a sign that they are in pain, or just indignation after we switch a light on. But squinting on just one side often means that something is wrong with that eye. Possible problems range from minor infections to serious injuries that can threaten our cat’s whole eye or even point to signs of illness elsewhere in their body. A squinting eye is never a problem to ignore, so read on to find out when need to get in touch with a vet.

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Cat Eye Anatomy

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Cat Eye Pupil

Cats’ eyes are a little different than human eyes but mostly work in the same way. The most obvious difference is the pupilthe black area at the center of the eye—which is slit-shaped instead of circular.

This should shrink down to a thin line in bright light, but in the dark, it will dilate (get bigger) to almost a full circle. If your cat’s pupils are always large even in bright light, or always slit-shaped even in the dark, then it is a sign something may be wrong.

Cat Eye Iris

The colored area around the pupil is called the iris. There is a whole range of normal colors in cats, including greens, blues, yellows, and oranges. You may also be able to see tiny blood vessels at the edge of the colored disc, which is quite normal. If your cat’s iris changes color or the blood vessels become more pronounced, it can be a sign of illness.

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Cat Eye Sclera & Conjunctiva

The white area around the edge of the eye is called the sclera. If this changes color or the blood vessels in the area become more apparent, they can be signs that something may be wrong.

The pale pink membranes around the eye are called the conjunctiva. They may become bright pink or even red if the eye is inflamed and can swell up so they come in front of the eye itself.

Cat Eye Cornea

The transparent dome that covers the eye’s surface is called the cornea. It is not easily visible in normal cats, but if there is damage to the eye or illness of another kind, you can see it more easily. It may become cloudy and faintly blue (edema), or blood vessels may start growing across the surface (neovascularization). Any changes to the cornea can be a sign of serious issues.

Cat Eyelids

Cats, like most other mammals (except humans), have three eyelids. The first two are the upper and lower lids (same as we have) but the third eyelid is a pink membrane that usually sits at the corner of the eye nearest the nose. If the eye is sore or damaged, this third eyelid may pop out to cover the surface of the eye.

Cat Eyelids
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Why Is My Cat Squinting One Eye?

There are many reasons why cats may squint with one eye. However, in almost all cases, the reason that your cat is squinting is that his eye is very sore.  Some of these conditions are more serious than others, but almost all of them need treatment by a vet.

1. Cat Trauma

A cat squinting in one eye is commonly caused by trauma. This is especially common if your cat goes outside, but can happen to indoor-only cats, too. It commonly happens after fighting with other cats or wildlife or by running into a piece of furniture or fencing.

As well as squinting, you may also see discharge from the eye, which can be clear and runny like tears or thicker and green-yellow like mucus. There may also be redness and swelling of the tissues around the eye, and your cat’s third eyelid may be visible.  Sometimes you will be able to see a scratch on the surface of your cat’s eye; it might look like a small dent.

If you think your cat’s eye has been damaged in this way, you should see a veterinarian as soon as possible since it can get worse quickly if it becomes infected, and your cat could lose their sight.

2. Cat Eye Infection

Infections are another common cause of a squinting eye. These infections are usually viral (“cat flu”), bacterial, or a mixture of the two. Viral infections can be caught from another cat or from virus particles brought into the house on objects like clothing or shoes. They can also occur when a virus your cat is carrying (usually herpesvirus) reactivates when your cat is stressed or ill for another reason.

The signs of an infected eye are similar to those seen with trauma. You may see a discharge (either runny or sticky), redness, and swelling, and the third eyelid may be covering part or all of the eye. Viral infections may also cause sneezing. You should see a veterinarian if you think your cat may have an eye infection.

3. Foreign Body in Cat

Cats may squint in one eye if something is trapped in the eye. We can see all kinds of “foreign bodies” in cat eyes, but common ones include thorns, cat claws, and grass awns. Sometimes, you can see these objects in the eye, but sometimes they are hidden under the eyelids.

If your cat has a foreign body in their eye, it is usually very painful, and they may be reluctant to open the eye at all. There may be swelling of the tissues around the eye, and the third eyelid may be covering part or all of the eye. The eye may be very watery, or (if the object has been there for some time) there may also be a bacterial infection causing a thick, sticky discharge.

If you suspect your cat may have a foreign body in their eye, it is an emergency, and you should see a veterinarian immediately. If you delay treatment, not only will your cat be in a lot of pain, but you risk permanent damage to the eye, which can cause blindness or even mean that the eye needs to be removed.

cat with eye infection
Image Credit: AI geba, Shutterstock

4. Cat Entropion

Entropion is where one of the eyelids (usually the lower one) starts to roll inwards. The hairy skin is rubbing on the surface of the eye, which is very painful and can damage the eye’s surface. It can also lead to infections. It can happen for many reasons and may affect cats of any age.

Cats with entropion will have very sore eyes and may not want to open them. They will also have a discharge from the eye, which may be clear and runny or thick and yellow/green. There may be a lot of swelling around the eye, too.

If you suspect your cat may have entropion, you should see a veterinarian, as this condition is very painful. Generally, surgery is required to stop the eyelid from rolling into the eye.

5. Cat Uveitis

Uveitis is inflammation in the front part of the inside of the eye, between the cornea and the iris. This may cause the eye to look cloudy or hazy, and occasionally, the bottom of the eye may be filled with sediment—either red (if there is bleeding) or white/yellow (if there is infection and pus). There is often no discharge from the eye, though sometimes the inflammation causes the eye to appear “watery”.

Unlike many other causes of cat squinting, uveitis is often caused by something in other parts of the body, such as:

  • Severe infections
  • Cancer
  • Diabetes
  • High blood pressure
  • An auto-immune condition

It can also be caused by severe blunt trauma to the eye. As uveitis can be a sign of serious illness, any cat suspected of having it should be checked by a veterinarian.

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What to Do if Your Cat Is Squinting One Eye

There are many reasons why cats may squint in one eye, and it can be difficult to work out the cause at home. Generally, a trip to the veterinarian is needed. Eye problems can quickly worsen, and delay risks your cat’s sight.

orange cat with squinted injured eye
Image Credit: Dariusz Sankowski, Pixabay

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Frequently Asked Questions (FAQ)

Is a Cat Squinting One Eye an Emergency?

Some causes of cat squinting need urgent treatment, or you risk the cat losing the eye. Others are less critical but still very painful for the cat and need treating promptly to avoid suffering.

You should make an emergency appointment if:
  • You think there may be something trapped within the eye.
  • The clear surface of your cat’s eye (the cornea) appears “dented” or otherwise damaged.
  • You cannot see your cat’s eye beneath the swelling.
  • Your cat is constantly rubbing at the eye.
  • Your cat appears withdrawn or has other symptoms of illness.

How Can I Help My Cat Without Going to the Vet?

If your cat has a sore, weeping eye, you can gently clean it to remove any built-up discharge from around the eye. To do this, boil some water, pour it into a dish, and let it cool. Then, dip a clean cotton towel in the water and use it to wipe around your cat’s eye gently.

This will help prevent the discharge from building up and may make the eye temporarily more comfortable but is unlikely to fix the underlying issue. You should still see a veterinarian after cleaning the eye.

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If you think something is trapped in your cat’s eye, DO NOT attempt to clean it or remove the object since you may make things worse. You should arrange an emergency appointment with your veterinarian.

Can a Cat Eye Injury Heal by Itself?

Some minor injuries will heal by themselves, but unfortunately, at home, you cannot tell which issues are minor or more serious. Any issue causing squinting will also be very painful for your cat. You should always see your veterinarian for pain relief so your cat does not suffer. The vet will also examine them to look for signs of more serious damage to the eye.

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Weeping eyes in cats are rarely caused by life-threatening issues but are often very painful and need treating promptly to avoid your cat’s suffering. Some injuries can threaten your cat’s vision or even risk the eye needing to be removed. If your cat is squinting one eye and you suspect there is a problem, rapid treatment will give them the best chance of preserving their vision and keep them as comfortable as possible while they heal.

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