Uveitis means inflammation of the uvea, the middle layer of the eye made up of the iris, the ciliary body that produces the fluid inside the eye, and the choroid that feeds the retina. That layer is packed with blood vessels, which makes it a natural landing site for infections, immune reactions and tumour cells travelling in the bloodstream. In cats, uveitis is one of the most common painful eye diseases and, according to Cornell University’s feline health team, the disorder most often behind feline blindness.
Why It Is Not Just a Red Eye
Conjunctivitis sits on the surface of the eye. Uveitis burns inside it, and the signs follow that difference. A cat may squint, hold one eye half shut, avoid bright rooms, hide, or simply sleep more than usual. The eye often looks hazy or blue-tinged, the pupil shrinks instead of dilating, the third eyelid slides up over the eye, and the iris may darken, look mottled, or fill with blood. Because cats hide pain well, many owners notice a change in appearance long before they notice discomfort, which is one reason the condition is often discovered only once complications have set in.
Signs That Mean Same-Day Care
- Squinting, pawing at the face, or rubbing the eye against furniture
- A cloudy, hazy or blood-filled eye, or a sudden change in iris colour
- A constricted pupil, or one pupil clearly smaller than the other
- Thick, watery or bloody discharge with redness around the eye
- A swollen or bulging eye, which can signal rising pressure inside the eye
- Bumping into objects, hesitating on stairs, or missing the food bowl
Any of these warrants an examination the same day. A blinded, painful eye that is left alone cannot be undone later, and pressure that keeps climbing can destroy the optic nerve within days.
Uveitis Is a Symptom, Not a Diagnosis
Finding the cause matters because the treatment plan depends on it. Veterinarians sort the possibilities into causes outside the eye and causes inside it. Outside causes include blunt trauma such as a road accident, cat-fight injuries, foreign bodies, and reflex inflammation triggered by a corneal ulcer or a damaged surface. Inside causes are far more common and include infectious agents such as feline infectious peritonitis, feline leukaemia virus, feline immunodeficiency virus, feline herpesvirus, toxoplasmosis, Bartonella and systemic fungal disease; cancer, especially iris melanoma, lymphoma and the aggressive sarcoma that can form years after eye trauma; high blood pressure; and immune-mediated disease.
Idiopathic uveitis, where no trigger is ever found, is common in cats, and middle-aged male cats are over-represented. Antibody testing has to be read carefully, because many perfectly healthy cats carry antibodies to toxoplasma and feline coronavirus, so a positive result does not prove that organism is the culprit.
How the Workup Fits Together
| Test | What it answers |
|---|---|
| Fluorescein stain | Is the cornea ulcerated? This must be checked first, because steroid drops are unsafe over an ulcer |
| Tonometry | Pressure is usually low in uveitis and high in glaucoma, so it separates the two |
| Blood pressure | Hypertension in older cats can cause both uveitis and retinal detachment |
| FeLV/FIV, toxoplasma and fungal testing | Whether an infection is driving the inflammation |
| Bloodwork, urinalysis, imaging | Whether there is systemic disease or cancer behind the eye |
| Ocular ultrasound, aqueous sampling | What the cloudiness is hiding, and occasionally a definitive diagnosis |
Treatment Direction and Long-Term Care
The goal is to shut down inflammation quickly, keep the pupil mobile, and treat whatever started it. Anterior uveitis is usually managed with topical anti-inflammatory drops, either a corticosteroid such as prednisolone acetate or, when steroids are risky, a topical non-steroidal option. An atropine-type pupil-dilating drop relaxes the painful muscle spasm of the ciliary body and helps prevent the iris from sticking to the lens. Posterior uveitis, and severe inflammation that eye drops alone cannot control, usually requires systemic treatment. When an infection is identified, it is treated specifically; when high blood pressure is the trigger, lowering blood pressure is as important as the eye drops themselves.
Uncontrolled uveitis causes lasting damage: adhesions between the iris and lens, secondary glaucoma, cataracts, lens dislocation, retinal degeneration, and in the worst cases a shrunken, blind and painful eye that has to be removed. At home, most cats need an Elizabethan collar so they cannot scratch the surface, a written schedule for drops that may need spacing out, and follow-up rechecks to taper treatment slowly. Tapering too fast is a common reason inflammation rebounds.
Never use leftover human or dog eye drops in a cat. If one eye has turned cloudy, painful or blood-filled, that is a same-day veterinary problem.