Our cats may squint at us for a lot of reasons. It can be a gesture of affection, or 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.
Cat Eye Anatomy
Cats’ eyes are a little different than human eyes, but mostly work in the same way. The most obvious difference is the pupil – the black area at the center of the eye – which is slit-shaped instead of circular. In bright light, this should shrink down to a thin line, 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 this is a sign something may be wrong.
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 – this is quite normal. If your cat’s iris changes color, or these blood vessels become more obvious, this can be a sign of illness.
The transparent dome that covers the surface of the eye is called the cornea. This 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 (neo-vascularization). Any changes to the cornea can be a sign of serious issues.
Sclera and 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 obvious, then these 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 also swell up so they come in front of the eye itself.
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 normally 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.
Why Is My Cat Squinting One Eye?
There are many different 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.
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, as these can get worse quickly if they become infected, and your cat could lose their sight.
Infections are another common cause of a squinting eye. These infections are usually viral (“cat flu”), or 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 that your cat is carrying (usually herpesvirus) reactivates when your cat is stressed or ill for another reason.
The symptoms of an infected eye are similar to those seen with trauma – you may see 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. If you think your cat may have an eye infection, you should see a veterinarian.
3. Foreign Body
Cats may squint in one eye if they have something 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 itself, but sometimes they are hidden under the eyelids.
If your cat has a foreign body in their eye, this 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 some bacterial infection present causing a thick, sticky discharge.
If you suspect your cat may have a foreign body in their eye, this 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 removing.
Entropion is where one of the eyelids (usually the lower one) starts to roll inwards. This means that the haired skin is rubbing on the surface of the eye, which is very painful and can damage the surface of the eye. It can also lead to infections. It can happen for many different reasons and may affect cats of any age.
Cats with entropion will have very sore eyes, and may not want to open them at all. They will also have 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.
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 squinting, uveitis is often caused by something outside the eye. Illnesses in other parts of the body, such as:
It can also be caused by severe blunt trauma to the eye.
As uveitis can be a sign of serious illness, any cat that is suspected of having uveitis should be checked by a veterinarian.
What to Do for a Cat With an Eye Injury
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 get worse, and delay risks your cat’s sight.
Is a Cat Eye Squinting an Emergency?
There are lots of reasons why a cat may squint in one (or both) eyes. Some of them need urgent treatment, or you run the risk of the cat losing the eye. Others are less critical, but still very painful for the cat, and so need treating promptly to avoid suffering.
How Can I Help My Cat Without Going to the Vet?
If your cat has a sore, weeping eye then you can gently bathe it to remove any built-up discharge from around the eye. To do this, boil some water, then pour it into a dish and let it cool. Then, dip some clean cotton wool in this water and use it to gently wipe around your cat’s eye.
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.
If you think there may be something trapped in your cat’s eye, DO NOT attempt to bathe it or remove the object as 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 and which are 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.
Weeping eyes in cats are rarely caused by life-threatening issues, but are often very painful and need treating promptly to avoid your cat suffering. Some injuries may threaten your cat’s vision or even risk the eye itself needing to be removed. Rapid treatment will give your cat the best chance of preserving their vision, and keep them as comfortable as possible whilst they heal.
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Featured Image Credit: Adina Voicu, Pixabay
- Cat Eye Anatomy
- Why Is My Cat Squinting One Eye?
- What to Do for a Cat With an Eye Injury
- Is a Cat Eye Squinting an Emergency?
- How Can I Help My Cat Without Going to the Vet?
- Can a Cat Eye Injury Heal by Itself?