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Cats Eyes Always Dilated [Should You Be Worried?]

Eyes are incredible and intricate body parts, enabling vision and the ability to observe developments in our environments. Dilation serves a crucial purpose too. Ensuring vision remains clear even in low light conditions. For cats, this could not be more crucial. This ability has enabled them to become successful hunters in the wild and to keep themselves safe from other, larger foes. But what about our domestic and pet cats? Particularly if you notice that their eyes always seem dilated? Is it something to be concerned with? Is there anything that you need to do? Well, here is everything you are going to want to know. 

So, why are my cats’ eyes always dilated? Constant or prolonged dilation of pupils can be a symptom or sign of an underlying health condition or blindness in cats. A cat’s eyes should be in a normal, relaxed state most of the time. While low-light conditions and emotions such as excitement and anxiety can cause the pupils to dilate, this should only last for a short period or until the conditions change. 

Ultimately, you are going to need to seek the advice of a vet if you are concerned.  

Particularly if you have monitored your cat’s eyes for a while and noticed that they do not return to their relaxed state given a period of time.

They will be able to help you identify the route of the issue and give some suggestions as to what to look into. 

But, of course, dilation does serve a purpose and should be expected from time to time.

The next few sections will walk you through that.

Before we turn to the appropriate response.

So, stick around. Your cat’s health could depend on it!

Why Do Cats Eyes Dilate?  

Cats dilate their pupils to regulate the amount of light that enters their eyes. The technical term for this is mydriasis. Humans do this as well, but it is especially important for cats because it contributes to their incredible night vision. 

In fact, studies have revealed that a cat’s pupils can expand up to ten times wider than a human pupil!

In bright light, the pupil appears as a narrow vertical slit and expands to be fully round in dim or dark conditions. 

By expanding their pupils at night, cats can absorb the maximum amount of light possible in order to improve their vision. 

The pupils may also change shape and size depending on your cats’ mood. 

So, by observing your cats’ eyes (as well as other parts of the body), you can get a gauge for how your cat is feeling. 

Pretty cool, huh? 

Here are the most common behavioral reasons for dilated pupils in cats: 


Cats are predators at heart, and playing with a wand toy or a fake mouse allows our domestic cats to activate those deeply ingrained instincts. 

Cats must be vigilant when hunting in the wild, which is accomplished by pumping adrenaline through their muscles. 

This allows cats to react quickly and also causes your cats’ pupils to dilate, giving them better vision to catch that tasty mouse!


This can be a little confusing for kitty owners to understand. How can opposing emotions, such as excitement and fear, both cause the same pupil reaction? 

How can you tell them apart? 

To make matters worse, the culprit responsible for dilated pupils in fearful cats is also the same – adrenaline! 

When a cat is startled or scared, it produces large amounts of this hormone which triggers the fight or flight response. 

This puts all muscles on alert and gives your feline companion the best chance of survival. 

Cats that are afraid will dilate their pupils to ensure they can properly assess the danger, just as cats that are excited will dilate their pupils to see their prey better.

Perhaps the easiest way to determine whether your cat is fearful or excited is to look at the surrounding environment as well as your cat’s other body language indicators.

If your cat is bouncing after a toy and swishing its tail, you can be sure that he or she is excited.

Conversely, your cat may have been startled by something if it runs and hides or curls its tail around its body in a protective manner. 

Because nervous cats are more likely to lash out in defense, it is best to wait for your kitty to calm down before attempting to interact.


Most cats become aggressive when they feel cornered or fearful. 

You will be able to tell if a cat has become aggressive by its eyes. 

Anxious cats avoid eye contact, whereas aggressive cats give a direct stare that is perceived as threatening and confrontational. 

An aggressive cat may also squint its’ eyes slightly to protect them from potential injury.


Cats are notorious for concealing signs of pain or illness, which can make It difficult for owners to determine when something is wrong.

However, if you notice your cat’s pupils are dilated for more than a couple of hours, especially if it is accompanied by other worrying behaviors such as a loss of appetite or excessive vocalizations, then it may be time to see the vet.

Why Would A Cat’s Eyes Remain Dilated? 

Your cats’ eyes should not be dilated for more than two hours (unless you live in a very dark house, of course!). If your cats’ eyes are constantly dilated for long periods, this could indicate a medical issue that needs addressing. 

In Kittens or Newly Adopted Cats

If you’ve recently adopted a new cat and notice his pupils are frequently fully dilated, this could be due to overstimulation. 

We all know that cats do not deal well with change! 

So, a new environment filled with novel stimuli is likely to either overexcite your cat or make him very nervous – both of which will result in dilated pupils. 

For this reason, you must confine your cat to one room at first. 

Then, once he appears comfortable, you can start introducing him to other areas of the house. 

Anxiety is a relatively common condition in cats, with 20-25% of all cats suffering from it.

If a cat is seen wandering from room to room with dilated pupils and a hunched posture, it is important that you try to investigate the cause and make adjustments as soon as possible. 

Prolonged anxiety can lead to more serious health problems down the line. 

Some cats are naturally nervous, but you can alleviate the symptoms by using calming scents and herbal remedies. 

Maintaining a strict, dependable routine will also help to keep your cat calm and content.

In Older Cats

Elderly cats are particularly prone to blindness, especially purebred cats. 

As your cat’s vision deteriorates, the pupils may remain dilated in an attempt to absorb more light and aid his vision.

Blindness can be permanent or temporary, depending on the cause. 

Kidney issues, eye infections, and feline herpesvirus can all cause temporary blindness.

A cat that is losing its sight may also display other symptoms such as: 

  • Clumsiness 
  • Walking with whiskers held low to the ground 
  • Easily startled by sudden noises 
  • Excessive vocalizations 

The good news is that cats can learn to live with the condition.

There are, however, a number of things you can do to make the transition easier, such as providing obstacle-free paths to food and water. 

Should I Be Worried If My Cat’s Eyes Are Dilated? 

Most of the time, dilation is an entirely natural, healthy, and normal response. However, if you do notice dilation frequently or for prolonged periods, you should at least get your cat checked over by a vet. 

That way they can inspect, investigate and treat any conditions that may be contributing to the dilation.

They can run tests on your cat and give you a better understanding of the cause.

They may suggest some environmental changes; which may be a more simple and straightforward fix.

Or they may identify and help treat the below.

Medical Causes Of Dilated Pupils

Here are some of the more common medical causes of dilated pupils in cats: 


A cat that has ingested a toxin will have dilated pupils. Unfortunately, our homes and gardens contain a wealth of deadly toxins such as chemicals and certain plants.

So, it is important to always be vigilant. Other symptoms of toxicity to watch out for include:  

  • Vomiting  
  • Diarrhea  
  • Lethargy  
  • Muscle tremors  

If you suspect your cat has consumed a toxin, you must get him to the vet immediately as the toxins need to be drained from the body.


A cat has hypertension if its blood pressure is 160/80 mmHg, which is relatively common in older cats.

The pain and discomfort caused by the condition can lead to dilated pupils, as well as blood in the urine and extreme thirst.

Iris Atrophy

This is another condition that affects older cats and is characterized by the thinning of the iris.

Unfortunately, iris atrophy is not treatable, but it’s usually nothing to worry about.

The only thing you may notice is that your cat becomes more sensitive to bright lights as it will be unable to contract its pupils.

So, make sure you provide plenty of dark areas in your home and ensure your cat can easily escape from bright lights.

Ocular Tumors

Your cats’ pupils could be dilated because a tumor is pressing on the muscles and vessels behind the eye.

This can be incredibly painful, so you must seek advice from a vet if you notice any of the following symptoms (aside from dilated pupils): 

  • Inflammation  
  • Discharge from the eyes 
  • Cloudy eyes 
  • A misshapen iris 

Eye Infections

Cats can develop eye infections, which cause their pupils to dilate. They can be bacterial or the result of an allergy or irritation.

General eye infections can be treated with eye drops, but ulcers on the eye may need to be surgically removed.   

If you notice that only one of your cats’ eyes is dilated, then he has something called anisocoria. 

The condition itself is not considered to be serious, but this does depend on the underlying cause.

Both toxicity and ocular tumors can cause anisocoria, as well as glaucoma, or an eye injury. 

If your cat has suddenly developed anisocoria, you should speak to a vet to be on the safe side! 

What To Do If Your Cat’s Eyes Are Often Dilated

Your cat’s eyes can be dilated for many reasons, but prolonged dilation is often caused by stress or a health condition. So, you should make an appointment with your local vet to determine the cause, as some health issues can be fatal if left untreated. 

The most common medical cause of dilated pupils is hypertension which can be treated with regular medication.

However, because there are so many different potential causes, you should seek professional advice as soon as you can.

In the meantime, it is important to remain calm as cats can pick up on signs of stress in their human companions.

At the same time, perhaps look into your home and the environment your kitten/cat is living in.

Can it be optimized in any way?

Do you need to alter the lighting or make your kitten/cat feel more comfortable and confident?

Just consider older cats are more likely to suffer from detrimental health conditions, but they can affect cats of any age and breed.


Cats’ eyes dilate.

That’s entirely natural.

Although, they should only do so briefly.

So, if they always seem dilated, there is something going on.

It could be something that you can address, or it may be something that requires medication.

Either way, liaising with a vet is always advised.

At least to rule out any health conditions.

Other than that, by keeping a close eye on your feline companion, you should be more able to pick up on any subtle warning signs that could indicate a problem. 

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