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What Are These Squiggly Lines In Cats’ Eyes?

If you’ve recently peered into your feline friend’s face, you may have noticed a couple of squiggly lines on the outer parts of its eyes.

Generally speaking, the squiggly lines you see in your cat’s eyes are its major iridal vessels. Most of the time, these vessels are healthy and normal to see, but there may be instances where they become problematic.

A cat’s eye is made of a dense network of blood vessels of different sizes and pigmentation. Sometimes, certain vessels may seem larger than their counterparts, causing concern for pet owners.

It’s important to know how to differentiate between healthy iridal vessels and a health hazard for your fuzzy friend.

While a squiggly line in your cat’s eye could be a healthy vessel, inflammation or other abnormalities may point to a health concern within your pet.

Some issues may be hereditary, while others stem from diseases, trauma, parasites, gene mutations, or other causes. To best ensure that your cat is healthy and happy, make sure to schedule a video call with a veterinarian today.

Why Is There A Squiggly Line In My Cat’s Eye?

The squiggly line in your cat’s eye could be iridal vessels, a parasitic eye worm, corneal damage, or eye inflammation.

These situations show differing symptoms, but it may be difficult to determine the cause of your cat’s eyes’ squiggly lines without professional assistance. Keep on reading to learn of the general ways you can distinguish what you’re seeing within your cat’s eyes.

Iridal vessels are normal blood vessels commonly found on the outside area of the eyeballs. They are prominent on the bottom half of cat eyes, although they may go full circle around the eye.

Iridal blood vessels are often easy to spot, but may not be noticeable from far away. If you suddenly see your cat’s iridal vessels and notice they are enlarged or red, you may be seeing signs of eye inflammation, called uveitis.

Various types of eye inflammation can affect the different layers of your cat’s eyes.

Eye inflammation usually leaves your cat’s eyes red, watery, and uncomfortable. It can be caused by corneal damage, an illness like pink eye, or even a parasitic eyeworm condition called thelazia.

You’ll be sure to notice that your cat seems to be uncomfortable due to the inflammation, but you may not know its root cause.

This will be determined by a veterinarian professional who may suggest distinct treatment options, such as antibiotics, anti-parasitic medications, and/or an Elizabethan collar to prevent rubbing of the eyes.

Can Cats Have Worms In Their Eyes?

Thelaziasis is an infection caused by a parasitic eye worm called Thelazia callipaeda. This parasite egg is deposited into the infected animal’s eyes through a species of fruit fly.

Thelaziasis affects thousands of pets annually and can be treated by a veterinarian; however, if left untreated in worst-case scenarios, the parasites could cause blindness in the animal.

This common fruit fly species feeds off of the secretions of your cat’s eyes. This is one of the reasons it’s particularly important to provide adequate eye care to your feline, especially if your cat wanders outdoors.

After feeding, the fruit fly lays its eggs within your pet’s eye and the parasitic egg eventually grows into a worm that lives within the eye’s conjunctival sac, under the eyelids, and within the tear ducts.

You may be able to see the small, whitish worms moving in a fast, snake-like motion across your cat’s eye.

Symptoms of Thelaziasis include inflammation, cloudy corneas, watering and itching of the eyes, and slow-healing sores within the eyes. A veterinarian can confirm the diagnosis after applying a local anesthetic to thoroughly examine your pet’s eyes.

Some veterinarians may choose to remove the parasites with forceps during the visit, while others may opt for oral anti-parasitic treatments. If removed immediately, most cats make a full recovery with no lasting damage from the parasite.

How Can I Tell If My Cat Has Eye Problems?

Your cat will likely notice any eye problems before you do, and its behavior can be a direct sign that something is wrong. You can look out for certain actions like rubbing or squinting, as well as any movements or behaviors that are peculiar or new to your pet.

Another red flag is if your cat is suddenly avoiding sunny areas or bright light. Preventative measures to keep your cat’s eyes healthy include taking care of, cleaning, and observing its eyes regularly.

Additional symptoms of eye problems in your cat can include over-watery eyes, gooey or extensive eye discharge, third eyelid issues, inflamed corneas, pink lining around the eye, blinking excessively, or pawing at the eyes.

You may choose to wait a day or two to see if the problem goes away on its own before deciding to take your cat to the vet. If any of these symptoms are paired with coughing or trouble breathing, be sure to bring your cat to an emergency veterinary service immediately for treatment.

To maintain healthy eyes, we recommend keeping up with required annual vaccinations, keeping your cat in a well-ventilated and clean area, and checking up on your cat’s eyes frequently.

Always check for changes in discharge, color, redness, shape, or light sensitivity. Every so often you can also wipe away your cat’s eye discharge with a cotton ball wet with water, but this should not be done regularly unless discussed with a vet.

Try to also avoid over-the-counter washes or drops unless previously discussed with and prescribed by your vet.


Almost every healthy cat has some noticeable squiggly lines within its eyes, called iridal vessels. If these vessels become inflamed, however, this could point to a bigger problem with your cat’s health, such as pink eye, corneal damage, or a different bacterial or respiratory infection. Moving squiggly lines could also be a sign of parasitic worms within the eye. Be sure to consult with your veterinarian as soon as possible to ensure you are treating your cat if needed.