Chorioretinitis in Cats

Chorioretinitis is rarely fatal but usually occurs as a symptom of a more serious disease. To properly treat it and prevent further eye damage, the underlying cause must be identified and treated. Cats with chorioretinitis or symptoms of vision changes should be seen by a veterinarian.

Chorioretinitis is a condition of the eye that results from inflammation of certain layers of the eye. It can affect cats, dogs, and other companion animals. The condition is usually related to a systemic infection that causes issues throughout the body, although it can occur on its own. The condition occurs when specific layers of the eye swell. The layers affected are the retina, which is used to translate images into messages for the brain, and the choroid, which contains the blood vessels of the eye. Because the choroid contains a heavy concentration of blood vessels, it is especially susceptible to infections carried in the blood. When infections or other factors cause these layers of the eye to swell, they cause damage, vision changes, and pain.

There are few obvious symptoms of chorioretinitis. In most cases, the condition is caught as part of the veterinarian’s routine monitoring of the eyes during treatment for other infections or diseases. During eye examinations, all layers of the eye are observed for changes that might indicate chorioretinitis is occurring. Some symptoms may be observed without an eye exam.

Observable Symptoms:

• Color change
• Eye pain
• Pawing or rubbing the eyes
• Changes in the eye’s appearance
• Cloudy, liquefied, or otherwise abnormal vitreous
• Bleeding in the eye

Symptoms Found by Eye Exam:

• Scarring
• Inflammation
• Retinal detachment
• Tracts from invasive larvae
• Glaucoma 

The primary cause of chorioretinitis is swelling of the eye’s choroid and retina layers. This inflammation is often a side effect of another disease the cat is facing. Genetics, including inherited abnormalities, can result in chorioretinitis, putting cats with relatives that had the condition at a greater risk. Chorioretinitis can also be a result of eye infection, invasion by parasites or insect larvae, physical trauma to the eye, or nutritional deficiency.

As chorioretinitis is often a symptom of other diseases, your veterinarian will have to consider a wide range of potential causes, if the primary infection is not already known. It is even possible that no underlying cause will be determined. 

Some possible primary conditions include:

• Systemic infections caused by bacteria or viruses
• Fungal infection
• Autoimmune disorders
• Hypertension or blood pressure disorders
• Metabolic diseases
• Toxicity or poisoning 
• Cancer

A diagnosis of chorioretinitis can usually be made by close examination of the eye under light using a magnifying tool called an ophthalmoscope. Your pet will first have their pupils dilated and will then be observed under a light in a darkened room in a traditional eye exam. This will allow the veterinarian to observe the cat’s eye and pinpoint issues in the choroid or retina. Changes, lesions, scarring, clouding and other clinical signs observed in the cat’s eye will aid in diagnosing chorioretinitis.

To determine the underlying cause or infection if not known, your veterinarian will conduct several other tests. Be prepared to discuss your pet’s medical history, genetics, and other symptoms they are experiencing. A physical examination will occur, and a series of tests may be required. Blood, urine, and spinal fluid may be collected for analysis. Your veterinarian might also use X-rays or other imaging to look for signs of diseases or infections that could cause chorioretinitis. 

The treatment for chorioretinitis is generally based on the underlying condition causing it. Your veterinarian will determine the best course of treatment for your cat once they have diagnosed the cause. For example, chorioretinitis related to a bacterial infection will be treated with antibiotics. Some treatments are geared specifically toward relieving the symptoms of chorioretinitis. Treatments for this condition are often outpatient, but your pet may be hospitalized if the underlying cause is severe. 

• Nonsteroidal anti-inflammatories: Also called NSAIDs, this category of anti-inflammatory can be prescribed even before the exact cause of the chorioretinitis has been identified. This drug helps to reduce the swelling and pain and should not have a negative impact on the underlying condition. The appropriate dose will be determined by your pet’s size. 
• Corticosteroids: This category of drugs also has a superior ability to reduce swelling and control the immune system’s reaction to the condition. They are not safe to give to your pet until infectious causes have either been ruled out or treated successfully. 
• Medicated eye drops: Your veterinarian may use one of several types of medicated eye drops to treat your pet. Depending on the type of drops used, they may help to reduce swelling or might have an antimicrobial effect.

Successful recovery from chorioretinitis requires appropriate treatment for the inflammation and the disease or infection that caused it. Many pets will make a full recovery without any long-term vision concerns. Cats with severe or long lasting chorioretinitis may experience detachment of the retina, severe scarring, or destruction of portions of the eye, which will leave them with irreparable vision changes. Limited vision, complete blindness, and loss of the eye could occur in one or both eyes. 

While your pet is undergoing treatment and recovering, be sure to follow your veterinarian’s instructions completely, including returning for any requested follow-up visits. Monitor your pet closely for signs of the condition worsening. Check their eyes frequently for changes and bleeding. See your veterinarian immediately if these occur. 

Even if your pet experiences partial or complete vision loss, they can still lead a full life once they grow accustomed to the situation. Be sure your cat has a safe space with easy access to their food, water, and litter. Avoid making major changes to your home’s layout while your cat adjusts. Block their access to anything that could be hazardous, including stairways and slippery surfaces. Speak to your cat frequently in a normal tone to soothe and reassure them. Most animals will adapt quickly to their new limitations and learn to rely more heavily on their other senses.