My cat has red eyes: why? Is it serious?

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It is not normal for a cat to have redness in one or both eyes. Some eye diseases and conditions can cause red eyes and other symptoms as well. Red eyes in cats should be taken seriously and it is recommended that you do not wait to take your pet to the veterinarian as this can be a serious problem. Let’s look at it in detail.

Red eyes in cats: the causes

Here’s what can cause red eyes in a cat.


The eyeball is joined to the eyelids by a membrane called the conjunctiva. If the conjunctiva is inflamed, it is called conjunctivitis. It is a common condition that causes reddening of the affected eye, usually associated with swelling of the eyelids.

Conjunctivitis in cats can be caused by:

A foreign body in the eye (grain of sand, spikelet, dust…),
A badly implanted eyelash that causes irritation,
A parasitic attack,
An allergy to pollen or dust (allergic conjunctivitis),
A virus,
A fungus,
A bacterium.

A local treatment based on eye drops is enough to treat some conjunctivitis, but it does not always work 100%. In addition to eye drops, the veterinarian can prescribe an antibiotic or any other treatment depending on the origin of the conjunctivitis.
An obstruction of a tear duct

This is a condition of the lacrimal glands that is most commonly found in brachycephalic cats, i.e. feline breeds with a very short or crushed muzzle. In this case, the cause of the obstruction is morphological. But sometimes this problem is due to a foreign body in the eye which becomes red and very watery.

The veterinarian prescribes a specific lotion so that the cat’s eyes can be cleaned regularly with a sterile compress. This lotion is instilled directly into the diseased eye.


A cat’s eyes may be red when the tunica vascularis of the eyeball is inflamed. Other symptoms include:

Contractions of the constrictor muscle of the iris leading to a reduction in the diameter of the pupil: the adapted term is myosis,
Localized pain of varying degrees.

A local anti-inflammatory in the form of eye drops may be sufficient to treat the cat. If the cat has a systemic infection, the veterinarian will prescribe an oral antibiotic and/or antifungal treatment.
Nictitating membrane prolapse or third eyelid

Prolapse (also known as procidence) is an absolute veterinary emergency and can be identified by a small pink mass that forms in the inner corner of the eye when the third eyelid is protruding. It is a sign that the ligament that holds the gland of the third eyelid in place has broken.

Generally, the cat does not suffer. However, the eye will water and sometimes pus will leak out. The prolapse can also cause conjunctivitis with reddening of the eye. In addition to treating the problem that caused the prolapse, the veterinarian often has to perform surgery to reposition the prolapsed organ.

An eyelid disorder

The upper and lower eyelids of cats can be the site of various conditions such as:

Entropion, which causes irritation of the cornea by the rubbing of the eyelashes because the free edge of the eyelid turns inward, Ectropion, a term designating the eversion of an eyelid or tissue, i.e., its turning outward, which has the direct consequence of exposing the conjunctiva Ectropion is quite rare in cats.

In either case, the veterinarian must perform surgery.


This is an inflammation of the cornea, the natural lens of the eye. The cat’s eyes are red because keratitis is usually associated with conjunctivitis. It causes the cornea to become vascularized and lose its transparency. Keratitis can be due to:

An irritation,
An infection,
Keratoconjunctivitis sicca (KCS), i.e. chronic drying of the conjunctiva (dry eye),
A trauma (blow, scratch…).

The opacity of the cornea must alert the owner of the animal. It is fundamental that the cat is taken care of urgently because in the absence of treatment, the keratitis can involve serious consequences such as the perforation of the cornea or a corneal ulcer. This can lead to vision problems and even blindness.


This is a serious eye disease because if the cat is not treated as soon as possible, it can lose its sight. The main symptoms of glaucoma are :

A red eye,
Strong local pain,
An increase in pressure,
A dilated pupil,
The formation of a bluish halo around the iris,
Blood vessels that appear swollen,
Difficulty moving around,
The cat will not let the owner pet its head because it is suffering from migraines.

The veterinarian must first lower the IOP (Intra-Ocular Pressure), because the optic nerve is damaged as it increases. Then he must identify the exact cause of the glaucoma in order to treat the underlying problem. Finally, he prescribes an eye drop, painkillers to relieve the pain and an anti-inflammatory medication if necessary. Sometimes, the ultimate solution is the drainage of the intra-ocular cavity through a surgical procedure. The laser gives good results if it is performed without delay.

Redness of the eye in cats: it can be serious

It is clear that some eye diseases or conditions are serious. As soon as a cat’s eyes become red, it is useless, and even dangerous for the animal to wait several days before consulting a doctor, thinking that things will spontaneously return to normal. Some owners even decide to put eye drops in their cat’s eyes when they have not received any medical advice. Self-medication is not recommended

No matter how superficial the cat’s eye condition may seem, it is important to seek medical advice immediately. The slightest negligence in this area leads to a delay in treatment. We have seen that in some cases, the cat can become blind, and this is irreversible.

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