Optic Nerve Swelling in Dogs

Optic Neuritis in Dogs

Optic neuritis refers to a condition in which one or both of the 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 and usually affects only dogs younger than three years of age. The secondary form of optic neuritis, however, in which the disease is secondary to another disease, such as central nervous system (CNS) dysfunction, is more common.

Optic neuritis can affect both dogs and cats. If you would like to learn more about how this disease affects cats please visit this page in the PetMD 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 dog’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.


The prediction of a disease’s outcome in advance

optic disk

A blind spot in the eye


A group of organisms made up of only one cell; a one-celled animal


The layer of the eye that is charged with receiving and processing images


Something that is related to the whole body and not just one particular part or organ


Anything having to do with the eye or care of the eye


A medical condition that results when the nerves become inflamed


In veterinary terms, used to refer to the front of the body.


Extreme loss of blood


Relating to a disease of unknown origin, which may or may not have arisen spontaneously


A bundle of fibers that are used in the process of sending impulses through the body


Term used to imply that a situation or condition is more severe than usual; also used to refer to a disease having run a short course or come on suddenly.

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