Optic Neuritis is an inflammation of the optic nerve, which leaves the back of the eye and exits into the brain at the back of the bony orbit of the skull. The optic nerve serves the very important function of getting visual information from the eye into the brain and to the visual cortex, located in the back of the head.
Sometimes this condition is referred to as Retrobulbar Neuritis, in order to reflect that it is located behind the eye.
Typically, a patient arrives in their optometrist’s office for an urgent appointment with symptoms of vision disturbances and ocular pain, especially when she tries to move her eyes. Sometimes the pain is enough to cause her to move her entire head rather than follow a target with her eyes only, even though she has it in only one eye.
On examination, both eyes appear to be normal in appearance, especially if this is the first time the patient has experienced anything like this. Visually, there may be blur or "fogging" of sight, also reported as "blackening" or a "hole" in the visual field, again, usually in only one eye. Color vision in the affected eye may be described as a washed-out appearance that may be more noticeable when looking at red objects. The pupils may also have unequal responses to light, with the affected eye being slower to respond.
Changes in the vision follow the onset of the pain within several hours or a few days. Females more often than males present with optic neuritis.
A comprehensive vision examination will reveal the changes in the vision noted above, but otherwise the eye will appear normal, especially if the patient has not had such an attack previously, and if the exam is taking place early in the process. Because the inflammation is located behind the eye instead of inside it, the eye itself will look quite normal in most cases.
Optic Neuritis has been commonly associated with the autoimmune disorder, multiple sclerosis, (MS) which manifests in about half of patients presenting with it. In fifteen to twenty percent of patients who later develop multiple sclerosis, the optic neuritis is their first symptom. Another autoimmune disorder, neuromyelitis optica, can also be the underlying cause.
Autoimmune diseases are the result of a person's immune system attacking part of their own tissues. Multiple sclerosis causes damage to the myelin sheath that provides insulation for nerve fibers, causing the messages to and from the brain from moving as fast or as efficiently as they normally would. Neuromyelitis Optica is similar, but attacks the optic nerve and the spinal cord, instead of the brain.
Infections, such as Lyme disease or tuberculosis can also trigger optic neuritis, as well as the medication ethambutolol, which is used to treat TB. This often puzzling condition can be mimicked by tumors pressing on the nerve in its passage from the eye to the brain, nutritional deficiencies or radiation therapy.
A neurologist will order an MRI scan of your head to either diagnose or rule out multiple sclerosis or other conditions. In MS, there are characteristic changes to the white matter of the brain.
Although anyone with these symptoms would be very concerned, the prognosis is quite good for recovery of normal vision; most patients will regain their vision within weeks to months following onset, even without treatment of any kind.
Even for those patients who exhibit brain lesions on MRI which are seen in multiple sclerosis, those who do experience this as their first symptom usually experience a relatively mild form of MS.
Optic neuritis will usually resolve on its own without any treatment, although intravenous steroids are sometimes prescribed to reduce the inflammation in the optic nerve.
If an MRI shows characteristic changes in the brain that are associated with MS, a patient may consider treatment with one of the new interferon medications to prevent new lesions.