Optic Neuritis

The diagnosis of Optic Neuritis is based on the patient’s medical history, as well as the absence of other diseases which can cause visual loss. The eye exam may help in showing abnormalities at the back of the eye in the optic disc, which is the part of the optic nerve visible using an instrument called an ophthalmoscope. There may be abnormalities of visual field testing, colour vision, testing, and visual acuity testing that aid in the diagnosis.

Occasionally, other diseases have to be considered in diagnosing Optic Neuritis, but these are usually apparent during the history and examination. For example, some people who are older than 50 experience a sudden loss of vision in one eye which is due to a problem with blood flow to the eye, and not due to inflammation.

Testing helps to exclude other diagnoses and evaluates the likelihood of other diseases. An MRI study of the brain and orbits (the eye sockets) with gadolinium contrast may confirm the diagnosis of acute demyelinating optic neuritis. In addition, patients whose MRI scans show two or more areas of demyelination in the brain are now known to have a higher risk of going on to develop MS than patients with few or no such areas.

• MRI scans let doctors look at the brain and spinal cord by way of a very powerful magnet that shows inner tissues. Gadolinium helps to indicate inflammation in the brain and optic nerve. Gadolinium should not be used in patients with significant kidney disease or known allergic reactions to dyes used in contrast material.
• Lumbar puncture is usually not necessary for isolated optic neuritis, but is sometimes used in assisting with the diagnosis of multiple sclerosis. If there are unusual features of the Optic Neuritis-for example, patient age of less than 15 years, bilateral Optic Neuritis, or symptoms suggesting infection-lumbar puncture may be needed to check for other diseases.
• Blood tests may be necessary in some people with optic neuritis depending on the situation. Diseases which can be checked with a blood test include, but are not limited to,lupus erythematosus, temporal arteritis, sarcoidosis, syphilis, and Lyme disease.
• The visualevoked potential test is non-invasive and measures how electricity is conducted along visual pathways. The test calls for the patient to watch a checkerboard pattern on a screen while electrodes monitor brain activity. With Optic Neuritis, there may be slowing in one or both optic nerves.
• Ocular coherence tomography (OCT)is a new non-invasive technique to evaluate the back of the eye. The test can measure the nerve fiber layer at the back of the eye. OCT’s role in diagnosis of Optic Neuritis is still unclear.

Optic Neuritis may resolve spontaneously without treatment. However, if visual function is poor, a course of IV methyl-prednisolone (a steroid medication) with a tapering course of oral steroids afterwards has been shown to speed recovery of visual function. The usual course is three days of IV steroids followed by a few days of tapering medication. Side effects of steroids include:

• Difficulty sleeping
• Stomach upset
• A metal taste
• Anxiety or irritability
• Increased glucose levels (particularly in diabetics)
• Thrush (a fungal infection)

Long-term steroids have other risks. Low dose oral prednisone is no longer used as it is not effective for optic neuritis.

If patients have multiple areas of demyelination on the MRI scans of the brain, there is some evidence that using medications that are effective in relapsing-remitting multiple sclerosis may make it less likely that the patients will develop Multiple Sclerosis.

In general, Optic Neuritis improves in about 80 percent of patients over a few weeks. Some people have continued visual change, reduced colour vision, or more difficulty with night-time vision. Many have a complete resolution of their symptoms. Even if there is some residual vision loss, people regain functional vision and can read and pass a driving test.

Occasionally Optic Neuritis recurs and requires retreatment. A small group of patients has continued recurrence of Optic Neuritis and requires ongoing treatment. Over time, about 50 percent of patients with Optic Neuritis will develop other neurological symptoms suggesting Multiple Sclerosis. Patients with more severe Optic Neuritis may have a condition called Neuromyelitis Optica, which can be diagnosed with a blood test.