Optic neuritis refers to swelling or inflammation of the optic nerve. It is often associated with diseases causing demyelination (a loss of the protective myelin layer of the the nerve) of the optic nerve, but sometimes the cause is unknown. Multiple sclerosis (MS) is the disease most often associated with optic neuritis. It is not uncommon to have an episode of optic neuritis prior to being diagnosed with MS. In fact, optic neuritis is often the initial sign of MS.
Most patients with optic neuritis experience a sudden onset of decreased vision along with pain and soreness when moving the eye. Optic neuritis usually affects only one eye and may be a recurring problem with certain diseases such as MS.
The following symptoms of optic neuritis may not occur in all cases; however, they are the most common problems associated with the condition.
The eye care practitioner takes several factors into consideration when diagnosing optic neuritis. The problem may not always be readily apparent by examining the optic nerve, so special attention is paid to the patient's symptoms and other tests. Pain with eye movement is a hallmark symptom of optic neuritis. The eye care practitioner may evaluate the pupils' reaction to light and order tests such as: visual field, color vision, and imaging of the brain (MRI).
Since the Optic Neuritis Treatment Trial (ONTT), physicians have discovered that treating patients with intravenous steroid medication (but not oral steroids) reduces the risk of developing MS later on. This finding is very significant since approximately 50% of those who experience an initial occurrence of optic neuritis will develop MS. While this treatment has little if any impact on vision, it is important for overall health.
Optic neuritis characteristically improves over a period of days to weeks. For some, a complete recovery may take months.
Illustrations by Mark Erickson
With acknowledgement to St. Lukes Eye Hospital.