When to see a vet urgently
A new change in vision needs prompt assessment. Contact a vet immediately if:
- your cat suddenly seems blind, bumps into things or cannot find familiar routes;
- the pupils become noticeably different sizes or you can see blood inside the eye;
- the eye is painful or very red, or your cat keeps it closed;
- vision changes after an injury to the eye or head.
Do not wait for sight to return on its own: find a vet near you.
Overview
The ocular fundus is the inner surface at the back of the eye, which a vet assesses by ophthalmoscopy. It includes the retina, optic nerve and blood vessels. Changes may be associated with inflammation, circulatory problems, degeneration or injury. Diseases of the fundus often develop gradually without obvious signs and are only discovered during a specialist examination.
The retina converts light into nerve signals, and the optic nerve carries the information onwards. Blood vessels in the choroid support retinal function. Vision can therefore deteriorate in different ways: sensory cells may degenerate, inflammation may damage tissue or the retina may detach from its underlying layer. These diseases do not all need the same treatment.
The visible outside of the eye may look normal despite a change at the back. Managing well in a familiar home does not rule out impaired vision either, as a cat can use memory and other senses. Watching the eyes or the way your cat moves cannot reveal the condition of the fundus at home.
Causes
The most common causes of diseases of the ocular fundus in cats include:
- high blood pressure, often secondary to kidney failure or hyperthyroidism;
- inflammatory diseases, such as chorioretinitis and uveitis;
- infections, such as toxoplasmosis and viral diseases;
- injuries to the eye or head;
- congenital retinal abnormalities;
- degenerative processes, such as retinal atrophy;
- tumours of the fundus or optic nerve.
High blood pressure can cause bleeding, swelling and retinal detachment at the back of the eye. Eye damage associated with kidney disease or an overactive thyroid may therefore occur through raised blood pressure. Knowing about the underlying disease does not replace measuring blood pressure. High blood pressure may cause few signs for a long time, until damage to a target organ becomes apparent.
Chorioretinitis means inflammation of the retina and choroid. Uveitis is a broader term for inflammation of the eye's uveal tract and can affect the front or back of the eye. It may result from a disease within the eye or a problem affecting the whole body. Where necessary, finding inflammation therefore leads to a search for a systemic disease as well.
Risk factors
- older cats with other chronic diseases;
- certain breeds, such as Abyssinians, which are predisposed to retinal diseases;
- chronic high blood pressure or kidney failure;
- traumatic injuries.
Breed predisposition applies to particular diseases rather than every change in the fundus. For example, one form of progressive retinal atrophy is associated with a known genetic variant. Signs of an inherited disease may appear later in life, so normal vision as a kitten does not rule it out. Cats of other breeds and non-pedigree cats can also develop acquired retinal diseases.
Symptoms
Diseases of the ocular fundus in cats may cause:
- worsening vision and hesitant movement in familiar surroundings;
- dilated pupils that do not respond to light;
- sudden blindness;
- a squint or nystagmus, meaning involuntary eye movements;
- signs of an underlying disease, such as high blood pressure.
Nystagmus can also be associated with a disorder of the balance system or nervous system. Involuntary eye movements and unsteady movement do not, on their own, locate the problem in the fundus. As well as examining the eyes, the vet may assess neurological function, especially if your cat has a head tilt, falls over or circles.
In some cases, there are no visible symptoms and the diagnosis is made only by ophthalmoscopy.
Hesitation in dim light, changes in jumping or bumping into furniture that has been moved may reveal gradually deteriorating sight. You may notice the change suddenly even though the disease has been progressing for a long time. Tell the vet about earlier subtle changes and whether the problem seems to affect one or both eyes.
A dilated pupil alone does not identify the cause of the damage or show whether sight loss is permanent. Diseases affecting different eye structures can produce similar observations. Do not test vision at home by frightening your cat or putting them somewhere unsafe. Have any new change examined at a veterinary practice.
Consequences
Without treatment, diseases of the ocular fundus can lead to:
- permanent blindness;
- chronic eye inflammation;
- optic nerve atrophy;
- a substantial reduction in quality of life.
When the retina detaches, its normal connection to the underlying layer and part of its blood supply is disrupted. Even if it reattaches, damaged tissue may not regain function. In some situations, prompt treatment can preserve or restore vision, but the diagnosis alone cannot guarantee the outcome.
However, permanent visual impairment does not automatically prevent a good daily life. A cat can adapt to sight loss using other senses when the environment is safe and any pain or active disease is treated. Investigating an acute change in vision is a different matter from the long-term care of confirmed permanent blindness.
Diagnosis at the vet
To identify the disease, the vet may carry out:
- ophthalmoscopy;
- blood pressure measurement;
- ultrasound of the eyeball;
- blood tests for infections and chronic diseases;
- electroretinography, or ERG, to assess retinal function.
The examination also assesses the front of the eye, pupil responses and, where necessary, pressure inside the eye. Blood pressure and eye pressure are separate measurements. Raised blood pressure throughout the body can damage the retina, whereas glaucoma involves raised pressure inside the eye. Distinguishing between them affects treatment choices.
Ophthalmoscopy examines the structures and blood vessels of the fundus. Ultrasound can help assess the inside of the eye if the view is obscured or a problem such as detachment is suspected. ERG is a functional test of the retina. It may be used when degeneration is suspected, even before obvious changes appear in the fundus. It is not a routine test for every patient.
If an inherited disease is suspected, genetic testing may complement the eye examination. A particular test identifies only the genetic variant for which it was designed. A negative result therefore does not rule out all forms of retinal degeneration or acquired eye diseases. Genetic information can also help with breeding decisions, but does not replace examining a cat with symptoms.
Blood pressure is measured with the cat as calm as possible and with minimal restraint. Fear can affect the result. Fundus findings, the overall pattern of measurements and any kidney or thyroid disease are considered together. Blood tests aim to look for underlying causes suggested by the findings, rather than giving every cat the same set of infection tests.
Treatment and follow-up
Eye damage associated with high blood pressure requires treatment of the blood pressure and monitoring of the response. Any underlying disease is treated at the same time. Eye drops alone cannot correct high blood pressure throughout the body. Even if the reading is brought under control, existing retinal damage may remain permanent, so treatment goals are discussed according to the examination findings.
For inflammation, the aims are to relieve inflammation and pain and treat any identified cause. An infection may need targeted medicine, while an injury may require different treatment. How a medicine is given depends on which part of the eye it needs to reach. Do not start old eye drops on your own because a new symptom has appeared.
There is currently no treatment that restores vision in progressive inherited retinal degeneration. Supplements and vitamins have not been shown to stop it. This differs from a nutritional problem, such as damage associated with taurine deficiency. The diet is assessed, but a supplement cannot replace identifying the correct cause.
Follow-up monitors vision, eye structures, pain and blood pressure according to the diagnosed disease. Inflammation may need close monitoring because complications such as glaucoma or retinal detachment can develop. Tell the vet if the eye becomes redder or cloudier, or your cat starts avoiding having their head touched.
Daily life with a visually impaired cat
Keep food, water, the litter tray and routes through the home in familiar places. Avoid leaving new obstacles in these routes, and secure stairs and other places where your cat could fall. Speak as you approach so that touch does not startle them. Arrange outdoor access in a safe, supervised or enclosed environment where your cat cannot enter traffic.
Prevention
- regular eye examinations, especially in older cats;
- blood pressure monitoring;
- treatment of chronic diseases, such as kidney failure and hormonal disorders;
- prevention of injuries;
- vaccination against infections that can damage the eyes.
Your cat's diet should be nutritionally balanced and contain essential nutrients such as taurine. An unbalanced home-prepared diet or dog food is not suitable as a cat's long-term main diet. However, feeding cannot prevent every retinal disease: inherited degeneration and blood pressure damage need their own prevention or monitoring plans.
Vaccines protect against particular infections, rather than every disease of the fundus. Eye symptoms should not be considered harmless because a cat is vaccinated. Monitoring the eyes and blood pressure of older cats or those with kidney disease helps identify damage before you notice a clear deterioration in vision.
This article provides general information and does not replace veterinary care. If your cat develops symptoms, contact a vet.
Frequently asked questions
Can a disease of the ocular fundus be painless?
Yes. Retinal degeneration, for example, can impair vision without obvious eye pain. Inflammation or another eye disease present at the same time may be painful. The absence of pain therefore does not rule out a vision problem.
Can blindness caused by high blood pressure be reversed?
In some cases, prompt treatment can restore at least some sight. However, many cats are left with permanent damage. New sight loss needs immediate assessment so that a treatable cause can be addressed in time.
Does a normal genetic test rule out every eye disease?
No. The test relates to a particular genetic variant. It does not rule out every inherited disease or changes in the fundus caused by high blood pressure, inflammation or injury.
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
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- Hypertension Toolkit: Measuring Blood Pressure, Feline Veterinary Medical Association, accessed 2026-11-03.
- Progressive Retinal Atrophy (PRA rdAc) (Abyssinian), University of California, Davis Veterinary Genetics Laboratory, accessed 2026-11-03.
- Uveitis in Cats, VCA Animal Hospitals, accessed 2026-11-03.
- Feline Vision Problems: A Host of Possible Causes, Cornell Feline Health Centre, accessed 2026-11-03.
- Blind Cats, Cats Protection, accessed 2026-11-03.
- Vestibular Syndrome, Cornell Feline Health Centre, accessed 2026-11-03.
- Sudden Blindness, Cornell Feline Health Centre, accessed 2026-11-03.
- Progressive Retinal Atrophy in Cats, VCA, accessed 2026-11-03.