- Not a substitute for professional veterinary help.
Do your cat’s pupils suddenly seem huge for no reason at all? A cat’s pupils will dilate, or get bigger, to let more light inside—just like your eyes do. Your cat’s eyes might also dilate for other reasons, like excitement.
Most of the time, you don’t need to worry if your cat’s eyes dilate. This is pretty normal, and their pupils should shrink back to their normal size eventually.
In some cases, though, a health issue might be causing the dilated pupils. Read on to find out the difference between normal and abnormal feline eye dilation—and when it’s time to take your cat to the vet.
4 Reasons Your Cat Has Dilated Eyes
Non-medical causes of feline eye dilation include:
- Low light: A cat’s pupils will enlarge to help them see in dark environments. Cats can’t actually “see” in the dark, so to speak. Rather, their eyes have developed in such a way that they can use the light available to see much more clearly than you can!
- Play: During play, cats can get excited. This excitement prompts their sympathetic drive to dilate their pupils, explains Dr. Kat Pankratz, veterinary behaviorist at Animal Behavior Clinic. The extra light helps them (literally) keep their eyes on the prize.
- Anxiety or fear: If your cat feels anxious or afraid, the fight-or-flight response dilates their pupils in much the same way excitement does. This response helps your kitty stay alert in dangerous situations. Other signs of fear include tail-swishing, raised fur, crouching, or hiding.
- Catnip: A kitty who’s been into their catnip stash may have dilated eyes. You’ll probably also noticed some changes in their behavior, like rolling around on the floor, playfulness, licking, or rubbing on things.
If your cat’s eyes are dilated due to any of these reasons, their pupils should shrink back when they calm down or enter a brighter environment—or when the catnip wears off!
4 Medical Causes of Dilated Eyes in Cats
Certain medical conditions can cause your cat’s eyes to stay dilated. These health conditions can also lead to other vision issues.
Dr. Preston Turano, a veterinarian with Felix Cat Insurance, says any of the following medical reasons may cause a cat’s eyes to dilate abnormally:
- Hypertension: Cats with high blood pressure, or hypertension, often develop vision problems. In fact, the eyes are the most common organ that hypertension targets. High blood pressure can cause eye issues like retinal detachment, swelling, or bleeding. This condition can also cause vision loss.
- Glaucoma: Feline glaucoma prevents fluid from draining out of your cat’s eyes as it should. This fluid buildup puts pressure on the optic nerve. Left untreated, feline glaucoma can eventually cause blindness.
- Heart disease: Cats with heart disease may develop high blood pressure, which can, as noted above, cause vision problems.
- Medications: “Some medications can cause your cat’s eyes to dilate,” Dr. Turano says. For example, atropine can relieve eye pressure in cats with glaucoma, but it can also dilate your cat’s pupils and make them sensitive to light.
The outlook for each of these issues can vary, depending on your cat’s overall health and any treatment they get.
For example, sight loss caused by high blood pressure can sometimes be reversed with quick treatment. Vision loss from glaucoma is usually permanent, but early treatment may stop the condition from getting worse.
When to Visit a Vet for Dilated Cat Eyes
If you notice that your cat’s eyes are consistently dilated, especially in brighter spaces or when they’re resting, Dr. Turano recommends scheduling a checkup with your vet.
It’s also important to check for any symptoms that might accompany a medical condition, like glaucoma or high blood pressure. Examples of these symptoms include:
- Cloudy eyes
- Squinting
- One eye appearing larger than the other
- Bumping into things
- Behavioral changes, like a loss of interest in daily activities
- Disorientation or confusion
- Lack of balance
- Limb weakness
Checking Your Cat’s Vision
It can be a bit tricky to test your cat’s vision at home. After all, they can’t look at a chart and call out letters!
But if you’re concerned about their eyesight, you can check it by trying a few cat vision tests at home:
- The dazzle test: Briefly shine a light, like a small flashlight, into your cat’s eyes. A cat with normal vision will squint and look away. A cat with vision issues will likely keep staring ahead, with dilated pupils.
- The “menace response” test: Hold your hand palm out and slowly approach your cat’s eye—just don’t actually touch their eye! A cat’s “menace response” should kick in when they spot your approaching hand, and they’ll blink. A cat with eye issues may not react.
- The fall response test: Drop cotton balls, yarn, or something else that won’t make a sound when it lands on the ground. A sighted cat will watch the object fall. A cat with vision problems likely won’t realize that something fell, since they don’t have a sound to track.
That said, none of these methods provide conclusive proof. According to Dr. Turano, the most definitive way to check your cat’s vision is to bring them to the vet for an exam.
Takeaway
Feline eye dilation often doesn’t have a serious cause. A cat’s eyes will naturally dilate for many different reasons. If your cat is playing or has just come from a dark room, you don’t need to worry about their giant pupils!
But if your cat’s eyes seem dilated often, even when they’re resting or in a bright room, you’ll want to have your vet check them out. It’s especially important to visit the vet if you notice other concerning symptoms like eye cloudiness or changes in their behavior.
