Visual function at baseline and 1 month in acute optic neuritis: predictors of visual outcome.

OBJECTIVE: To identify cutpoints for visual measures at baseline and 1 month predictive of abnormal 6-month vision that could be used as eligibility criteria in a clinical trial to test potential neuroprotection or myelin repair agents in patients with optic neuritis. To determine whether moderate-to-severe dysfunction in one or more visual measures at baseline or 1 month correlates with having major vision loss at 6 months.
METHODS: We used the Optic Neuritis Treatment Trial database to evaluate various cutpoints for baseline and 1-month vision levels that predicted abnormal 6-month vision. For selected cutpoints, we computed a 95% CI for positive predictive value and the required sample size if the cutpoint was to be used for clinical trial eligibility. We evaluated whether the degree of visual loss at baseline, 1 month, or change in visual function from baseline to 1 month correlated with 6-month visual acuity, contrast sensitivity, or threshold visual field.
RESULTS: The best cutpoints for baseline and 1 month were visual acuity <or= 20/50, contrast sensitivity < 1.0 log units, and visual field mean deviation <or= -15 dB. The same levels of visual dysfunction at 1 month, but not at baseline, correlated with having 6-month moderate-to-severe loss for each of these measures (p = 0.01). A trial could require as few as 100 subjects for an outcome variable of one or more abnormal measures. Cutpoints at 1 month were highly predictive of abnormal 6-month vision, but the proportion of patients who would be eligible for a trial would be small.
CONCLUSION: Provided data can be used either for the clinician to counsel patients on expected visual outcome or for designing studies to test therapies that might reduce the amount of permanent optic nerve damage due to optic neuritis in high-risk patients.