Anatomically, the uvea is the whole vascular layer: it consists of the iris, ciliary body and choroid proper. Posterior uveitis specifically means inflammation of the choroid. When inflammation also involves the front parts of the uvea, it is called panuveitis. Inflammation can permanently damage sight, but its effects depend on the location and extent of the damage.
When to see a vet urgently
Seek assessment without delay if your cat has any of these eye symptoms:
- Vision suddenly deteriorates or your cat starts bumping into objects.
- The eye is painful and your cat squints or keeps it closed.
- The eye is red or cloudy, or blood is visible inside it.
- The pupil's shape or size changes noticeably and your cat has difficulty finding its way around.
You can find a vet near you. Even an eye that looks quiet from the outside may need urgent examination.
Overview
The choroid supplies nutrients to the retina and supports normal eye function. Inflammation disrupts circulation, damages tissue and causes inflammatory fluid to accumulate. Posterior uveitis often progresses unnoticed and is frequently diagnosed only when complications arise.
The retina, which lies close to the choroid, receives light and helps form visual signals. Inflammation involving both the choroid and retina is called chorioretinitis. A small localised change does not always cause a visual problem that you can notice. Extensive inflammation or damage around the optic nerve can have a substantial effect on sight.
Old scars as well as active inflammation may be seen at the back of the eye. Distinguishing between them helps determine whether a change is currently progressing or is the result of previous disease. The eye's external appearance alone cannot establish this: the back of the eye must be examined with appropriate instruments.
Causes
The main causes of posterior uveitis in cats include:
- infections, such as toxoplasmosis, feline immunodeficiency virus (FIV), feline leukaemia virus (FeLV), coronavirus and herpesvirus
- fungal and bacterial infections
- systemic inflammatory diseases, including autoimmune diseases
- tumours in the eye or elsewhere in the body
- eye injuries
- consequences of previous inflammation in the front of the eye
This list does not mean that every infection detected is a direct cause of posterior uveitis. Eye inflammation associated with feline coronavirus may be part of feline infectious peritonitis (FIP), but ordinary coronavirus exposure is not the same as FIP. Toxoplasmosis can damage both the eye and other organs. However, most cats infected with Toxoplasma do not become visibly ill.
The cause of some cases of uveitis remains unclear despite investigations. Immune-mediated inflammation is assessed by excluding other possible causes, as there is no single confirmatory test. A tumour, an infection and immune-mediated inflammation require different treatment plans. An eye finding may therefore lead to investigations of the whole body as well.
Risk factors
Posterior uveitis occurs more often in cats that:
- have chronic viral infections
- are unvaccinated
- have a weakened immune system
- are older
- have cancer
There is limited cat-specific information on individual risk factors for posterior uveitis, and lack of vaccination or older age alone does not explain the disease. For example, clinical toxoplasmosis is more likely when immune defences are weakened, but the same risk pattern cannot be applied to every cause of inflammation. Vaccinated cats can also develop uveitis.
Main symptoms
Uveitis can develop unnoticed, but the following signs may suggest it:
- impaired vision and difficulty finding the way around
- an enlarged pupil or a change in pupil shape
- cloudiness or a change in colour at the back of the eye
- retinal haemorrhages
- sensitivity to light
- lethargy and reduced appetite when systemic disease is present
An enlarged pupil is not a finding common to all forms of uveitis. With inflammation in the front of the eye, the pupil may instead be small, and its shape may change because of inflammation or adhesions. Bleeding or cloudiness at the back of the eye is usually a finding made during veterinary examination, rather than something you can reliably check at home.
Impaired vision may show as difficulty using stairs, bumping into furniture or trouble finding the food bowl and litter tray. Signs can also be subtle. A vision problem need not be accompanied by heavy eye discharge, and a small amount of discharge does not indicate how severe the inflammation is.
Complications and consequences
Without treatment, posterior uveitis can lead to:
- glaucoma, or raised pressure inside the eye
- cataracts
- retinal detachment
- partial or complete blindness
- chronic pain and reduced quality of life
A cataract is clouding of the eye's lens. This differs from cloudiness caused by inflammatory cells elsewhere in the eye. The location of the cloudiness is established during examination because it affects further assessment.
Glaucoma can develop if inflammatory cells or scars left by inflammation interfere with the drainage of fluid from inside the eye. High pressure can then persist even if the inflammation otherwise settles. Pressure monitoring may therefore also be needed later.
Retinal detachment means that the retina separates from the tissue beneath it. In cats, possible underlying causes include high blood pressure as well as inflammation. The cause of sight loss therefore cannot be determined simply from the fact that the retina has detached. The chances of vision returning also depend on whether damage has already become permanent.
Diagnosis at the vet
Diagnosis is based on:
- ophthalmoscopy, an examination of the back of the eye
- measurement of pressure inside the eye, called tonometry
- blood tests to rule out infectious disease, such as toxoplasmosis, FeLV, FIV and coronavirus
- eye ultrasound when cloudiness is present
- a general examination to detect systemic diseases
The examination assesses both the front and back of the eye and, where necessary, both eyes, even if symptoms are visible in only one. Pressure in an inflamed eye may initially be lower than normal. Glaucoma developing later raises the pressure, so measurements taken at different stages may differ.
A general examination, blood pressure assessment and laboratory or imaging tests selected for the situation help distinguish inflammation from other diseases that impair vision. Eye ultrasound can investigate a detachment or mass, for example, when cloudiness prevents the back of the eye from being seen. A vet with expertise in eye disease may be involved in further investigations if necessary.
Infection tests are interpreted alongside symptoms and other findings. A positive coronavirus antibody result indicates exposure; it does not, on its own, establish FIP or the cause of eye inflammation. Toxoplasma antibodies are not interpreted as a simple yes-or-no answer either: different antibody types and the cat's clinical condition affect the assessment. IgG antibodies in a healthy cat may reflect an earlier infection.
Treatment and follow-up
Treatment aims to control inflammation in the eye and treat its cause. Posterior uveitis usually requires systemic medication, which acts throughout the body, so that the medicine can reach the back of the eye. Eye drops alone therefore do not meet all its treatment needs, although they may be needed for concurrent changes in the front of the eye.
The eye's own protective barriers affect how medicines enter its tissues. Inflammation can increase permeability, but these barriers start working more effectively again as healing progresses. Treatment selection and continuation are therefore assessed from the findings. Do not assume that all medication can be stopped because the eye's surface looks clearer.
Medication targeting an infection is selected according to the confirmed or reasonably suspected pathogen. Inflammation associated with a tumour or injury may require a different approach. The suitability of anti-inflammatory medication is assessed at the same time in relation to any possible infection and the cat's other health conditions. Do not start a medicine previously prescribed for another eye problem on your own initiative.
Follow-up examinations monitor eye pressure, possible adhesions and retinal problems as well as vision and inflammatory changes. Oral medication may also require blood tests to monitor side effects. Tell the clinic about new vomiting, changes in appetite or drinking, and marked changes in behaviour. Follow-up intervals are tailored to the severity of the disease and response to treatment.
The prognosis is better if the inflammation and underlying cause can be controlled before permanent tissue damage occurs. Severe or recurrent uveitis increases the risk of complications. As well as protecting sight, treatment aims to keep the eye free of pain. If sight has already been lost, your vet will still assess possible pain and the need for further treatment.
Prevention
The risk of posterior uveitis can be reduced through:
- vaccination against viral infections
- prompt treatment of eye and systemic diseases
- protecting your cat from injuries
- regular eye examinations, particularly in older cats
Vaccination does not protect against every cause of eye inflammation or replace investigation of eye symptoms. Toxoplasma exposure can be reduced by preventing hunting and avoiding feeding raw meat. Remember, too, that an eye finding in an ill cat can reveal a disease affecting the whole body: investigations should not be limited to local eye treatment.
What it means for owners
Posterior uveitis in cats is a serious condition that often progresses unnoticed and is detected late. Remember that any deterioration in vision, change at the back of the eye or unusual behaviour requires immediate assessment by a veterinary ophthalmologist. Detecting inflammation early helps preserve your cat's sight.
Frequently asked questions
Can posterior uveitis affect both eyes?
Yes. Uveitis can affect one or both eyes. Even if you notice a change in only one, your vet assesses the eyes and the possibility of disease affecting the whole body.
Does a positive coronavirus blood test mean FIP?
Not on its own. Antibodies may also be present in a cat without FIP. Diagnosis is based on a combination of findings, and further investigations are selected according to the cat's symptoms.
Why does posterior uveitis need more than eye drops?
A locally applied medicine may not reach a sufficient concentration at the back of the eye. Posterior uveitis usually needs systemic treatment, which acts throughout the body, as well as treatment of the underlying cause.
Can eye pressure be low during inflammation and high later?
Yes. Uveitis can be associated with low pressure, but inflammation interfering with fluid drainage can later cause glaucoma. Repeated eye pressure measurements help detect this change.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- Uveitis in Dogs and Cats, American College of Veterinary Ophthalmologists, accessed 2026-11-03.
- Uveitis in Cats, VCA Animal Hospitals, accessed 2026-11-03.
- Toxoplasmosis in Cats, Cornell Feline Health Centre, accessed 2026-11-03.
- GUIDELINE for Feline Infectious Peritonitis, European Advisory Board on Cat Diseases, accessed 2026-11-03.
- The Ocular Fundus in Animals, Merck Veterinary Manual, accessed 2026-11-03.
- Feline Vision Problems: A Host of Possible Causes, Cornell Feline Health Centre, accessed 2026-11-03.
- Routes of Administration for Ocular Medications in Animals, Merck Veterinary Manual, accessed 2026-11-03.