The Effect of Amantadine on Corneal Endothelium in Subjects with Parkinson's Disease

Objective: To evaluate the effect of amantadine on corneal endothelial cells in subjects with Parkinson's disease. Design: Cross-sectional study. Participants: A total of 169 subjects (169 eyes) taking amantadine orally for Parkinson's disease and the same number of age-and gender-matched controls. Methods: Endothelial indices were compared between the amantadine-treated and age-matched control groups. The amantadine-treated group was divided into 3 subgroups according to the cumulative dose and duration of treatment. Endothelial changes were compared between the amantadine group and the normal control group, and among subgroups. Main Outcome Measures: Slit-lamp biomicroscopy, central corneal thickness (CCT), endothelial cell density (ECD), coefficient of variation, and hexagonality. Results: The amantadine group had significantly lower ECD (mean +/- standard error; 2662.47 +/- 29.06 vs. 2784.72 +/- 25.89, P = 0.002), lower hexagonality (56.94 +/- 1.07 vs. 60.97 +/- 0.87, P = 0.004), and greater coefficient of variation (35.59 +/- 0.57 vs. 32.66 +/- 0.52, P = 0.000) compared with the age-matched control group. Longer duration and higher cumulative dose amantadine therapy led to a greater reduction in ECD (P<0.05) compared with the normal age-matched control group. Conclusions: Amantadine is more likely to have an effect on corneal endothelial cells in a dose-dependent manner when used long-term.