old cat with dilated pupils
Questions About Cats

Why Are My Cat’s Eyes Dilated All the Time?

Felines are easily stimulated animals, so an agitated cat will have dilated pupils. If your cat is experiencing feelings of excitement, or fear and anxiety, they’ll have enlarged eyes. But if your cat’s pupils are dilated all the time, it’s typically a sign of an underlying medical problem.

Why would a cat’s eyes be dilated constantly? This is a warning sign that your cat is physically or mentally uncomfortable. Medical explanations for dilation of the eyes in cats include hypertension, key-Gaskell syndrome, or chronic pain caused by arthritis. Alternatively, your cat may be living with anxiety, and thus in an endless state of awareness. This will prevent your cat from relaxing, and lead to behavioral issues.

A cat’s eyes tell us a great deal about how they’re feeling. They’re truly the windows to the soul. It’s pivotal that you understand what different feline pupil sizes represent, and how to respond.  This guide discusses the explanations for dilated pupils in cats, and when you should be concerned.

Why Do Cat’s Pupils Change in Size?

A cat’s pupils can change in size substantially. A human pupil can expand up to 15 times its smallest size. However, a cat’s pupil size can expand to a factor of 135.

Take a look at your cat’s pupils throughout the day, and you’ll see this at work. Your pet’s pupils may be slits at one point, and substantial orbs at others. The amount of light entering the eye is a significant factor. However, so does your pet’s physical and emotional health.

Variables in pupil size depend on the mood that your cat is in at any given moment. A lot can be read into a cat’s state of wellness by their body language. The size and shape of feline pupils are among the biggest giveaways of all.

Cat Pupil Size Meaning

While cats have a wide range of variable pupil sizes, feline eyes typically look one of three ways.

It’s vital that your cat’s eye varies in size throughout a day. Any permanent, fixed eye position is not a good sign.

As Michelson Found Animals explains, expect to see one of these in your cat. Your pet’s eyes will reveal a great deal about their state of wellbeing.

cats eyes don't constrict

Half-Closed Eyes, with Unremarkable Pupils

It suggests that your cat is completely relaxed and content in their surroundings.

If your cat appears this way, they’re likely enjoying a doze or planning a nap. The sight is most common after eating.

This appearance isn’t an invitation to pet your cat. They are relaxed, and physical contact may ruin that. Leave your cat alone, and wait for them to approach you.

Extremely Narrow Pupils

If your cat’s eyes have narrowed to slits, keep your distance. If accompanied by hissing or growling, your cat is agitated and will likely attack.

Even if your cat is silent, narrow pupils suggest that they’re in full-on hunting mode. They may have spotted prey in the distance, or they’re playing with a favored toy.

Whatever the reason, it’s best to stay out of the way. A cat with narrow eyes is going to pounce. If you get in the way, your toes or ankles may become the target.

Wide and Dilated Pupils

Dilated pupils denote a state of stimulation. This may be excitement, a response to fear or shock, or a sign of pain management.

Your cat’s eyes will be dilated at various points throughout the day. This is a good sign as it means that your pet has sufficient stimulation throughout the day. As long as they periodically return to normal, all is fine.

My Cat’s Pupils are Constantly Dilated

Your pet’s eyes should not be dilated permanently. Take your own eyes as an example. You will go about your day with your eyelids in a neutral position.

However, they’ll dilate on occasion. The same can be said for your cat. Some of the sensations that will lead to a cat’s eyes dilating include:

  • Surprise. If your cat is shocked or startled, their eyes will widen temporarily. A loud noise will have this impact.
  • Excitement. If your cat is excited because they’ve spotted prey, their eyes will dilate.
  • Changes to Light. Feline eyes are susceptible to light. Switch off a light, and your cat’s eyes will widen to absorb what little illumination remains.
  • Pain. A short, sharp shock of pain will cause a cat’s eyes to dilate. This could be because you stepped on their tail or foot, for example.

A healthy cat will have pupils that vary in size throughout the day. Their eyes should also be bright, and not bloodshot or watery.

Conditions That Cause a Cat’s Eyes to Be Dilated Constantly

There are medical issues that could cause your cat’s pupils to dilate. The most common include:

  • Hypertension
  • Dysautonomia (Key-Gaskell Syndrome or Feline Dilated Pupil Syndrome)
  • Constant and chronic discomfort, such as arthritis pain
  • Toxins have entered your cat’s bloodstream

Hypertension in Cats

Hypertension means that your cat has high blood pressure. As the Cat Clinic of Roswell explains, feline hypertension is often linked to an overactive thyroid and kidney problems.

In addition to dilated pupils, cats with hypertension are often restless and agitated. Some cats with hypertension also experience sudden onset blindness. The condition is usually diagnosed following blood and urine tests.

Feline hypertension is a severe condition, and must be treated as such. As discussed, kidney disease is often linked to hypertension. The heart will also be affected.

Hypertension can be controlled, and even cured. A daily medication will manage your pet’s blood pressure. If your cat manages to avoid a secondary concern, their prognosis is very encouraging.

Dysautonomia in Cats

Feline dysautonomia is comparatively rare, but it does occur. It is most likely to affect a young cat, aged younger than three.

Dysautonomia is a mouthful, but the name makes sense when considering the impact of the condition. Dysautonomia attacks the automatic nervous system, which is responsible for duties that take place without thought.

disoriented cat with dilated pupils

A cat living with dysautonomia will experience the following symptoms:

  • Vomiting and diarrhea
  • Difficulty urinating
  • Extreme sensitivity to daylight
  • Lethargy and depression
  • Coughing and streaming nose and eyes
  • Weak muscles, which are prone to wastage
  • Loss of appetite, and associated weight loss

As PetMD explains, dysautonomia can be challenging to treat. The cause of the disease is unknown, meaning it cannot be targeted. Due to the wide range of potential complications, cats with dysautonomia are unlikely to survive.

Chronic Pain in Cats

Your cat’s eyes will widen when they are in discomfort. This could be a short, sharp burst of sudden pain. However, they may be living with a chronic condition.

Arthritis is arguably the most common of these conditions. If your cat has musculoskeletal pain, every step will hurt them. This will cause their eyes to widen every time they attempt to move. Perhaps you’ve noticed that your cat’s back legs have become weak or shaky.

Arthritis can be managed, with the appropriate treatment. Rebuild your pet’s collagen through supplements, and seek painkilling medication. Massage and other hands-on therapies will also ease their discomfort.

In addition to these steps, make some lifestyle changes to accommodate your pet’s condition. Ensure that your cat has a soft, comfortable bed, and multiple water and feeding stations.

The less your cat has to move, the more comfortable they’ll be. They’ll still need to exercise, but unnecessary physical activity equals avoidable pain.

Toxicity in Cats

Dilated pupils are one of the many symptoms associated with toxicity. This could be something your cat has consumed, or the result of an animal bite. The latter could include venomous snakes or spiders, or even ticks and fleas.

Alongside always diluted pupils in cats, warning signs of toxicity include:

  • Drooling
  • Shaking and muscle tremors
  • Pale or yellow gums
  • Vomiting and diarrhea
  • Hyperactivity and nervous energy
  • Lethargy and depression

Some cat’s pupils will also dilate as a side effect of medication for an unrelated concern. If this is the case, speak to your vet. You may need to look into a change of medication.

Mental and Emotional Issues

If your cat has a clean bill of physical health but dilated pupils, the issue is emotional. Occasional dilation is perfectly healthy and normal. No change to the eyes, however, is problematic.

If your cat’s pupils are constantly dilated, your cat is in a constant state of awareness. This is worrying, as it means that your cat can’t relax. If they have any reason to feel vulnerable, a cat will always be on high alert.

The first step to resolving this issue is finding out why your cat is so anxious. Has something changed in their routine? Do you have other pets in the house that are bullying the cat? Are you surrounded by loud noises, or other external stimuli?

You need to soothe your cat, and calm their anxiety. If your cat is emotionally uncomfortable, they’re at risk of growing physically unwell. They will also stop eating, drinking, and sleeping.

Get your cat into a strict routine, so your pet understands their needs will be met. If they struggle to co-exist with other animals, ensure they have a safe space. If you live in a noisy area, apply calming scents and sounds to the home.

One of My Cat’s Pupils is Dilated All the Time

If a cat’s pupils are dilated to different sizes, it’s due to a medical condition called anisocoria. Anisocoria in cats is not a disease in and of itself, but it is a warning sign.

As VCA Hospitals explains, there are many reasons for anisocoria. These include:

  • A disease in the eye, or to the brain stem that impacts upon the eye
  • A traumatic injury to the eye, or to the brain stem that affects the eye
  • Scarification behind the eyelid
  • Feline leukemia (FeLV)

Any injury or trauma in a cat must be investigated by a healthcare professional. Don’t ignore an incident if your cat does not show any immediate signs of distress. Internal damage, or a delayed reaction, is always possible.

The most common disease that could impact upon a cat’s eye is glaucoma. This is a severe condition that places pressure on the eye. It left untreated, glaucoma can lead to blindness.

Why Are My Cat's Eyes Dilated All the Time?

Other diseases can cause fluctuating dilation in your pet’s eyes, with varying degrees of severity. Cancer is the most concerning of these potential explanations.

Feline leukemia is a condition that has an 85% mortality rate. Vaccination is the most effective protection against FeLV.

Do Dilated Pupils Mean That My Cat is Going Blind?

If your cat has constantly dilated pupils, they may be struggling with their eyesight. This is most common in senior cats, though some medical conditions can cause sudden onset blindness. This could be temporary or permanent.

This will be your cat’s attempt at improving their vision. They will widen their eyes in an attempt at letting in more light.

Alternatively, if your cat has lost their sight, their eyes won’t react to changes in light. They’ll also be in a constant state of high awareness. Without vision, cats rely on their senses of smell and hearing.

Most cats can adapt without their eyesight. You’ll need to make adjustments to your home.

My Cat’s Eyes are Dilated at Night

If your cat’s eyes dilate in dim light, it’s not a concern. All cats widen their eyes by night to utilize their night vision. This only applies to poor lighting. Your cat’s eyes should not be dilated all day.

The reason for a cat’s eyes dilating by night is to allow light into the eye. Cats are genetically hardwired to be at their most active at dawn and dusk. This is when their prey is plentiful.

If there is too much light for a cat to see properly, they’ll narrow their eyes. A smaller pupil means that less light can penetrate the eyes.

When light is dim, your cat will be keen to take in as much light as they can. This is how cats see so clearly in the dark. They won’t have 20/20 vision, but they’re unlikely to bump into a table.

Cat eyes tell us about how they’re feeling, so learn the habits of your pet. You should see a range of adjustments to a cat’s pupil size based on their environment.

Dilated pupils are not an illness in themselves. They are a symptom of another condition, however. Just how serious this depends on the health ailment.