Background: About half of multiple sclerosis patients present with optic neuritis (ON) as a clinically isolated syndrome (CIS). In the Optic Neuritis Treatment Trial study, 28% of patients with ON and an abnormal brain magnetic resonance imaging (MRI) did not have a relapse at the end of 15 years. It is still difficult to predict which CIS patients will go on to develop clinically definite multiple sclerosis and which will have a benign course.
Review summary: This review focuses on more advanced methods of detecting and quantifying ON in multiple sclerosis that have been developed in the past 15 years, especially on recent developments in optical coherence tomography measurement of the retinal nerve fiber layer and its role in monitoring axonal loss in the course of the disease. New clinical trial methods of measuring visual acuity include high-contrast visual acuity testing with the Early Treatment Diabetic Retinopathy Study charts, low-contrast letter acuity, and contrast sensitivity testing. More advanced neuroimaging techniques include magnetization transfer imaging and diffusion tensor imaging to quantify visual pathway lesions. Other tests of visual function, such as multifocal visual-evoked potentials and functional MRI, have been shown to be more sensitive than conventional visual-evoked potentials or MRI in detecting early, subtle visual impairment in ON and early recovery of visual function related to cortical plasticity. Newer agents are currently being investigated for CIS in ongoing clinical trials.
Conclusions: Better methods are being developed for the earlier diagnosis, monitoring, and treatment of ON. In the future, CIS patients may be stratified according to their risk of development of clinically definite multiple sclerosis and therefore, receive the appropriate treatment.