Memantine Treatment in Acute Nonarteritic Anterior Ischemic Optic Neuropathy: A Randomized Clinical Trial

To evaluate the effects of memantine on improving visual function in patients with acute nonarteritic anterior ischemic optic neuropathy (NAION) This was a prospective, double masked, randomized, clinical trial. The study involved 47 subjects with unilateral NAION of less than 8 weeks duration. Eligible patients were randomly allocated to take either memantine tablets (5 mg daily during the first week and then 10 mg daily for the next two weeks, 25 subjects) or placebo tablets (22 subjects). Baseline visual acuity (VA) tests, pattern visual evoked potential (VEP) and automated perimetry (SITA-standard 24-2) were performed. VA tests were repeated 3 weeks, 3 months and 6 months after initial visit. VEP and automated perimetry were repeated 3 months after initial visit. At baseline there was no significant difference between the two groups in terms of clinical and laboratory characteristics. After 3 weeks, 3 months and 6 months of treatment, best corrected visual acuity (BCVA) improved by -0.31±0.39, -0.49±0.47 and -0.53±0.48 logMAR in the memantine group respectively and -0.02±0.41, -0.09±0.60 and -0.05±0.67 logMAR in the placebo group respectively (P=0.024, P=0.025 and P=0.017). VEP results demonstrated a reduction of implicit time of -8.32±17.18 mS in the memantine group after 3 months, whereas in the placebo group it increased +5.7±21.60 mS (P=0.043). The change in VEP amplitude was not significantly different between the memantine and placebo groups (P=0.083). The effect of the memantine on mean deviation (MD) and pattern standard deviation (PSD) changes was not significantly different from that of the placebo (P=0.428 and 0.863 respectively). Treatment of patients who experience acute NAION with memantine may result in significant improvement in BCVA compared with no treatment. The VEP changes seen at 3 months may indicate improved transmission of impulses through the optic nerve.