Optic Nerve Swelling in Cats

By PetMD Editorial on Dec. 17, 2008

Optic Neuritis in Cats

Optic neuritis is a condition in which one or both of the cat's optic nerves are swollen, resulting in impaired visual function. The optic nerve, sometimes called the cranial nerve, is a nerve in the eye that takes visual information and transmits it to the brain. Optic neuritis affects the ophthalmic and nervous systems of the body.

The primary form of optic neuritis is uncommon; the secondary form, however, is more common and occurs secondary to another disease, such as those affecting the central nervous system.

The condition or disease described in this medical article can affect both dogs and cats. If you would like to learn more about how this disease affects dogs please visit this page in the PetMD pet health library.


Symptoms and Types

Optic neuritis may be a primary disease or a secondary disease, meaning it occurs due to the presence of another disease in the body, such as a central nervous system (CNS) dysfunction. Optic neuritis is secondary to systematic CNS disease because the optic nerve communicates with the outermost layers of the brain (subarachnoid space).

Symptoms of optic neuritis include acute (sudden) onset of blindness and partial deficiencies in vision. A physical examination can reveal blindness or reduced vision in one or both eyes, fixed and dilated pupils, and a diminished light reflex of pupils. An examination of the anterior surface of the eye cavity may reveal a swollen optic disk, or a focal hemorrhage.



As previously mentioned, primary optic neuritis is very rare, while secondary optic neuritis is more common. Causes of secondary optic neuritis vary greatly. Possible causes include neoplasm, which is an abnormal cell growth, such as a tumor; systemic mycoses (a fungal infection); a parasitic disease known as toxoplasmosis; or lead poisoning. In some cases, the disease is considered idiopathic, meaning that it seems to arise spontaneously from an obscure cause and no specific origin can be identified.


The diagnostic procedure in cases of suspected optic neuritis generally includes an analysis of cerebrospinal fluid (the clear protective fluid in the cranium, in which the brain floats), and an electroretinogram in order to investigate the functioning capacity of the eye’s retina. Additional diagnostic procedures may include a computed tomography (CT) or magnetic resonance imaging (MRI) scan, urine analysis, and full chemical blood profile for the presence of fungi, viruses, or protozoa that may be causing an infection. will need to give a thorough history of your cat's health, onset of symptoms, and possible incidents that might have preceded this condition in order to further aid your veterinarian in making a diagnosis.


Treatment for optic neuritis is directly dependent upon the underlying disease that led to the condition. Certain procedures and medications may be given if the primary disease is identifiable. If no specific cause can be identified, certain medications may still be prescribed by your veterinarian to help alleviate symptoms. The final prognosis for animals with optic neuritis is dependent upon the underlying cause of the disease.

Living and Management

Your veterinarian will schedule a follow-up visit to monitor the effectiveness of the treatment. If no primary cause can be identified and your pet is suffering from idiopathic optic neuritis, blindness or loss of vision may become permanent. Medication should be given as prescribed in order to prevent subsequent flare-ups.

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