All of the above conditions can have ophthalmic manifestations, but the majority of optic neuritis cases seen in clinical practice are either sporadic or MS related. Optic neuritis is the first demyelinating event in approximately 20% of patients with MS. It develops in approximately 40% of MS patients during the course of their disease.
Optic neuritis is characterized by loss of vision (or loss of color vision) in the affected eye and pain on movement of the eye (painful ophthalmoplegia). Less often, patients with optic neuritis may describe phosphenes (transient flashes of light or black squares) lasting from hours to months. Phosphenes may occur before or during an optic neuritis event or even several months after recovery.
The diagnosis of optic neuritis is usually made clinically, with direct imaging of the optic nerves showing evidence of optic disc swelling with blurred margins. The real contribution of imaging in the setting of optic neuritis, however, is made by imaging of the brain, not of the optic nerves themselves. MRI of the brain provides information that can change the management of optic neuritis and yields prognostic information regarding the patient's future risk of developing MS. The most valuable predictor of the development of subsequent MS is the presence of white matter abnormalities. Between 27% and 70% of patients (in various studies) with isolated optic neuritis showed abnormal MRI brain findings, as defined by the presence of two or more white matter lesions on T2-weighted images. Patients with two or more lesions may have up to an 80% chance of meeting criteria for MS within the next 5 years.
A gradual recovery of visual acuity with time is characteristic of optic neuritis, although permanent residual deficits in color vision and contrast and brightness sensitivity are common. The symptoms of optic neuritis will usually resolve without medical treatment, although continuing to take regular MS disease-modulating medication is usually helpful. An intravenous steroid or oral prednisone is sometimes recommended to speed recovery. A 3- to 5-day course of high-dose (1 g) IV methylprednisolone, followed by a rapid oral taper of prednisone, has been shown to provide rapid recovery of symptoms in the acute phase. However, IV steroids do little to affect the ultimate visual acuity in patients with optic neuritis.
Typically, patients begin to recover 2-4 weeks after the onset of the vision loss. The optic nerve may take up to 6-12 months to heal completely, but most patients recover as much vision as they are going to within the first few months.
For patients with optic neuritis whose brain lesions on MRI indicate a high risk of developing clinically definite MS, treatment with immunomodulators may be considered. IV immunoglobulin treatment of acute optic neuritis has been shown to have no beneficial effect. In severe cases, plasma exchange may be considered.
Krupa Pandey, MD, Director, Multiple Sclerosis Center, Department of Neurology & Neuroscience Institute, Hackensack University Medical Center; Neurologist, Department of Neurology, Hackensack Meridian Health, Hackensack, NJ
Krupa Pandey, MD, has serve(d) as a speaker or a member of a speakers bureau for: Bristol-Myers Squibb; Biogen; Alexion; Genentech; Sanofi-Genzyme