CONDITION
Uveitis
Uveitis describes inflammation inside the eye, affecting structures that lie beneath the outer surface: the iris, the ciliary body, and the choroid. These tissues are rich in blood vessels and immune cells, which means inflammation here can arise from infection, immune reactions, injury, or processes elsewhere in the body that have reached the eye through the bloodstream. Owners often notice a red or clouded eye, squinting, sensitivity to light, or a change in the appearance of the iris or pupil. The eye may look uncomfortable, and in some cases the surface can appear hazy or the pupil unusually small. These signs can develop quickly or build gradually, and they can affect one eye or both. This page explores what uveitis can look like from the outside, the range of processes that can trigger inflammation inside the eye, how the condition is investigated, and the approaches used to manage it. The aim is to help you understand what may be happening and what shape assessment and care tend to take.
Why this matters now
Uveitis is inflammation within the eye, affecting the uveal tract (the iris, ciliary body, and choroid). It occurs in both dogs and cats and can result from numerous underlying causes, both local and systemic. The condition is significant because untreated uveitis can lead to permanent vision loss, glaucoma, or other serious complications. Identifying the underlying cause is often as important as treating the eye itself, as uveitis frequently signals disease elsewhere in the body.
Uveitis can present acutely with sudden onset of a painful, red eye, or develop more insidiously with gradual changes. The inflammation disrupts normal eye function, causing protein and cells to leak into the fluid chambers of the eye. Without treatment, scarring and adhesions form between structures within the eye. Complications include secondary glaucoma (from blocked fluid drainage), cataracts, lens luxation, and retinal detachment. Chronic or recurrent uveitis carries the highest risk of permanent damage.
Signals & patterns
Early signals
Red eye
Redness of the sclera (white of the eye) or conjunctiva often develops with inflammation.
Squinting or holding the eye closed
Pain causes blepharospasm, where the eyelid is held partially or fully shut.
Excessive tearing
Watery discharge from the affected eye is common.
Cloudiness within the eye
The normally clear fluid chambers become hazy with inflammatory debris.
Pupil changes
The pupil may be constricted and respond poorly to light, or appear irregular.
Later signals
Colour change of the iris
Chronic inflammation can alter iris pigmentation.
Visible opacity or cataract
Secondary cataract formation clouds the lens.
Enlarged or bulging eye
Secondary glaucoma causes increased pressure and eye enlargement.
Shrunken eye
End-stage disease can result in phthisis bulbi (a shrunken, non-functional eye).
Vision impairment
Behavioural changes suggesting reduced vision in the affected eye.
Click to read about the biological mechanisms
How this is usually investigated
Diagnosis involves thorough eye examination and, often, investigation for systemic disease. Identifying the underlying cause guides treatment and helps predict outcomes.
Ophthalmic examination
Blood tests
Retroviral testing in cats
Chest and abdominal imaging
Aqueous or vitreous sampling
Options & trade-offs
Treatment aims to control inflammation, preserve vision, and address any underlying cause. The approach depends on severity, identified cause, and whether one or both eyes are affected.
Topical anti-inflammatory medication
Eye drops or ointments containing corticosteroids or non-steroidal anti-inflammatory drugs.
Trade-offs: Widely used for anterior uveitis. Frequency depends on severity. Corticosteroids are more potent but contraindicated if corneal ulceration is present.
Topical mydriatics
Eye drops that dilate the pupil and relax the ciliary muscle.
Trade-offs: Reduces pain and lowers the chance of adhesions forming between the iris and lens. Atropine is commonly used. It is a human medicine with no UK veterinary authorisation for dogs or cats, so it is prescribed under the veterinary medicines cascade. Dilating the pupil can worsen raised pressure, so atropine is not used where secondary glaucoma is present or where the pressure in an inflamed eye is not low. The bitter drops can cause marked salivation in cats.
Systemic anti-inflammatory medication
Oral or injectable corticosteroids or non-steroidal drugs.
Trade-offs: Necessary for posterior uveitis or severe cases. Duration depends on response and underlying cause. Systemic side effects are possible with prolonged use. Because infection or cancer underlies a sizeable share of cases, investigation for these generally comes before systemic corticosteroids are started.
Treatment of underlying cause
Specific therapy targeted at identified infectious or immune-mediated conditions.
Trade-offs: Needed for resolution in many cases. May involve antibiotics, antifungals, or immunosuppressive drugs depending on diagnosis.
Monitoring for complications
Regular assessment of intraocular pressure and lens clarity.
Trade-offs: Secondary glaucoma and cataract require early detection. Additional treatment may be needed if complications develop.
Common misconceptions
"A red eye is always conjunctivitis"
Whilst conjunctivitis is common, a red painful eye can indicate uveitis, glaucoma, or other serious conditions. Distinguishing between these requires examination, as treatments differ significantly.
"Uveitis only affects the eye"
Uveitis is frequently a sign of systemic disease. Investigation reveals an underlying condition that requires treatment beyond the eye itself in a substantial share of cases, although in many no cause is found.
"Once the eye looks better, treatment can stop"
Uveitis often requires prolonged treatment. Stopping too early risks recurrence and complications. Treatment duration is guided by examination findings, not appearance alone.
Related conditions
Lymphoma in Dogs
Lymphoma can cause uveitis when malignant lymphocytes infiltrate the structures inside the eye. In one referral series of 102 dogs with uveitis, lymphoma was the most common tumour found, in 17 dogs. Ocular signs may appear before or alongside other manifestations of lymphatic disease.
Feline Herpesvirus (FHV-1)
Feline herpesvirus mainly causes inflammation of the eye surface. Viral DNA and locally produced antibodies have been found in the fluid inside the eye of some cats with uveitis, which suggests that the virus may be associated with uveitis in some cats, although a causal role is not proven.
Diabetes Mellitus in Dogs
Cataracts secondary to diabetes mellitus are common in dogs and often develop rapidly. Lens material leaking from the cataract can cause lens-induced uveitis. Cats appear resistant to diabetic cataract formation.
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Feline Infectious Peritonitis (FIP)
Feline infectious peritonitis is one of the most frequently identified causes of uveitis in cats. In a UK referral series of 92 cats with uveitis it was the most common identified cause, in 15 cats, and the affected cats were young, with a median age of 1.4 years.
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Recognising that a painful, red eye warrants prompt assessment helps prevent complications from delayed treatment. Understanding that uveitis investigation may reveal systemic disease prepares owners for comprehensive testing. Being aware that chronic cases require ongoing monitoring supports long-term management. Noting any changes in eye appearance or behaviour suggestive of vision changes provides valuable information.
Last reviewed: 9 October 2026 · Dr Alastair Greenway MRCVS