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Swollen whites in a cat’s eye

Swollen whites in a cat’s eye

Swollen whites in a cat’s eye can mean many things. The white in the inner corner of the eye is called a third eyelid and is usually seen only peeking out ever so slightly. Its purpose is to spread tears evenly when a cat blinks. However, if you see the third eyelid clearly, or if it is covering a portion of the eye, there is a chance that there is a medical issue that needs addressing.

Swollen whites: what could they mean?

There are multiple reasons that the third eyelid may become more visible. Some of these reasons may be quite innocuous, but some may be quite serious.


Conjunctivitis is a common condition in cats. This may be due to bacterial or viral infections, or just pure irritation. It is seen as reddening of the conjunctiva (the delicate tissue around the eye) and is often accompanied by discharge from they eye. One may also notice some sneezing fits if it is associated with viral infections. The most common reason is indeed viral infections in the form of snuffles. Treatment is dependent on the underlying cause and an examination by a vet is vital to treat the condition quickly and effectively.

Corneal ulcer

A corneal ulcer occurs when there is damage or disruption of the outer layer of cells of the cornea (which is the clear membrane in the centre of the eye). Corneal ulcers are known to be very painful causing the eye to be drawn deeper into the eye socket. This causes the third eyelid to become more prominent. Your cat may keep its eye closed due to the pain. Corneal ulcers are caused by direct injury such as scratches during cat fights, grass awns or bacterial infections. They need to be treated promptly by a veterinarian with appropriate medications.

Haws syndrome

Haws syndrome is a poorly understood condition that causes the third eyelid of both eyes to start protruding. The eyelid looks normal, as does the rest of the eye. Cats often also show bouts of vomiting or diarrhoea coinciding with the first few days that the eyelid protrusions are noticed. We do not know what causes Haws syndrome. But the condition rarely requires any treatment (apart from treating the vomiting and diarrhoea), and the third eyelids return to their normal position after a few months.


Any condition that causes pain around the eye can cause swollen whites to become more visible. This does not always mean the third eyelid is directly affected or abnormal in any way, it just becomes more visible. Conditions that cause pain include uveitis (inflammation of the inner parts of the eye), glaucoma (increased pressure in the eye), corneal ulceration (as discussed before), abscesses behind the eye, and even growths. These conditions each have their own treatments and require a vet exam to determine the appropriate treatment.


There are many reasons for cats to become dehydrated. The most common reasons are renal failure, diabetes, liver disease, gastroenteritis, or kidney infections. But any systemic illness could result in dehydration. Dehydration causes the eyes to become more sunken into the eye sockets, often then resulting in protrusion of the third eyelid. The third eyelid and the eye itself appear normal. Dehydration is usually a sign of marked or severe illness and should be treated by a veterinarian as soon as possible. This involves treating the dehydration with a drip, as well as finding and addressing the underlying disease.

Swollen whites need veterinary examination

Treatment of conditions affecting the third eyelid are more often associated with treating the underlying disease and not just the third eyelid itself. Due to the various conditions that may result in the third eyelid becoming more visible, a vet examination is of utmost importance, and should be done promptly.

NEVER use human eyedrops on your cat. These can cause more damage and may not actually address the underlying condition. The only drops that may be used are artificial tears or lubricating drops. These may create more comfort but is unlikely to actually address the problem, which may lead to a delay in receiving the appropriate treatment.

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