Reasons Why Your Cat’s Eyes May Be Dilated

Dilated eyes of a calico cat

When your cat’s eyes are dilated, it can be scary. You’re afraid that there may be something seriously wrong with your feline friend and that his or her condition will worsen if you don’t act quickly to seek medical attention.

The good news is that cat dilation of the eyes usually isn’t serious, and you can use this guide to help figure out why your cat has dilated eyes and what you can do about it.


Stressful Events

Cats can develop dilated pupils in response to stress, either emotional or physical. If your cat’s pupils are enlarged, he may be suffering from acute stress. Causes of acute stress could include a new pet in the house, a change in family structure (such as divorce), a move to a new home, or even a loud noise like fireworks.

These stresses should resolve themselves over time—but if they don’t and your cat’s eyes remain dilated for more than two weeks, it could indicate chronic stress that requires medical attention.

This type of stress is often caused by an underlying illness, such as kidney disease or hyperthyroidism. The only way to know for sure is to have your vet perform a thorough examination.

Don’t forget to tell your vet about any changes you’ve noticed in your cat’s behavior; he may be able to detect subtle signs of distress. For example, if you haven’t seen him eat for several days, ask yourself whether something might be wrong.



Cats have very small nasal passages, which means bacteria and viruses can reach their eyes very easily. That’s why eye infections are one of the most common reasons why your cat’s eyes may be dilated.

Fortunately, cat eye infections are pretty easy to spot (and treat). Watch for excessive rubbing and pawing at your kitty’s eyes. If you notice these symptoms, take him to a vet immediately; he could have an infection that needs treatment before it gets worse.

If you notice any discharge coming from his eyes or if they start to look red or swollen, don’t wait—to see a vet as soon as possible. Also, keep in mind that there are several types of eye infections in cats, so make sure you know what type your cat has so you can get appropriate treatment.

The sooner you get treatment, the better off your cat will be. Eye Injuries: While injuries aren’t quite as common in cats as they are in dogs, they do happen sometimes. For example, my neighbor once stepped on her kitten by accident and hurt its eye pretty badly.


Other Causes

Not all dilated eyes in cats are caused by eye infections. If your cat’s eyes are showing signs of irritation, inflammation, or discomfort and don’t respond to antibiotics, your vet may suggest additional testing.

This could include a CT scan to look for tumors or neurological issues. Blocked tear ducts or corneal ulcers can cause dilated pupils that don’t respond to antibiotics, as well. While these conditions aren’t life-threatening, they do require treatment to prevent further complications.

In some cases, surgery is necessary to remove blockages or repair damage. But if you notice unusual changes in your cat’s eyes—or any other symptoms—it’s important to have him examined by a veterinarian right away.

Even if he doesn’t have an infection, he may need other treatments like medication or supplements. Early detection can make all the difference when it comes to treating eye problems in cats.


Ear Infections and Eye Irritations

Animals’ eyes can be very sensitive. Infections in their ears or eyes, for example, can cause an increase in tear production as well as redness of their eyes. If your cat is experiencing these symptoms and you are not sure why your vet may be able to help determine a solution.

Remember: if you see something wrong with your pet’s eyes or any other body part that concerns you, take them to a vet right away. It could save their life! 

Some things they might experience that cause eye irritation include dust and pollen (in humans), chemicals, microorganisms (like algae), some soaps and detergents, perfumes—anything irritating really.

They also have more pressure behind their eyeballs than we do on our own eyes—this means irritants will affect them faster than we! You can learn more about how cats’ eyes work here.


Lack of Sleep

Most people know that sleep is important for humans, but did you know it’s equally as important for your cat? Studies have shown that sleep deprivation leads to many health issues in cats (and humans).

Take a look at your cat’s eyes and check if they are dilated. If they are, it could be due to a lack of sleep or fatigue. Most dilation occurs in one eye rather than both. A good night’s rest should clear up most cases of eye dilation.

However, there are other possible reasons why your cat’s eyes may be dilated. The causes include:

Make sure your kitty gets plenty of rest by setting aside a quiet space just for him. Consider building him his own personal kitty fort with cushions, pillows, and toys – he will love it!

Cats need about 16 hours of sleep per day so give them what they need! Also, make sure to create an environment where he feels safe from any danger like predators or cars outside.


Older Age

If your cat is more than eight years old, it could be a sign of trouble. Dilated pupils in an older cat are always worrisome and should have an exam with a veterinary ophthalmologist, Dr. Jain says.

Diabetes: If you notice dilated pupils in conjunction with excessive thirst and urination, weight loss, or polyuria (excessive urination), there’s a good chance that diabetes mellitus may be at play.

If cats lose their vision due to diabetic retinopathy, they will often develop nystagmus (rapid involuntary eye movements) and/or retinal degeneration, which can cause their pupils to become dilated, she explains.

It’s important to note that these symptoms can also be caused by other conditions such as liver disease or kidney failure. So if you suspect your cat has any of these issues, make sure to visit your veterinarian for further testing.

Infection: Bacterial infections can lead to inflammation in one or both eyes—which may result in dilated pupils. If one pupil is larger than another, I would suspect infection because [the infection] tends to affect both eyes equally, Dr. Jain says.

In rare cases, glaucoma can cause a cat’s pupils to dilate as well. Trauma: A blow to your pet’s head could result in trauma-induced dilation of its pupils.

In fact, trauma is one of the most common causes of nystagmus (those rapid involuntary eye movements) in cats and dogs alike, according to Dr. Marcello Lanzi, a veterinary ophthalmologist at Red Bank Veterinary Hospital in New Jersey.

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