Detecting Retinal Vigabatrin Toxicity in Patients with Partial Symptomatic or Cryptogenic Epilepsy

Purpose. Detecting retinal vigabatrin toxicity in patients with partial symptomatic or cryptogenic epilepsy can be challenging because of preexisting visual field defects secondary to a structural abnormality in the brain or lack of collaboration. The aim of this study was to measure the retinal nerve fiber layer thickness (RNFLT) with optic coherence tomography (OCT), as well as contrast sensitivity, color vision, and perimetry, in patients with partial symptomatic or cryptogenic epilepsy on vigabatrin, and to determine the efficacy of these tests as markers of vigabatrin-related retinal damage in these subgroups of epileptic patients. Methods. The study involved 38 patients with either partial symptomatic or cryptogenic epilepsy and 16 healthy individuals comprising the control group. At the time of the study, 14 of the patients were using vigabatrin, 10 were receiving sodium valproate monotherapy, and 14 were on carbamazepine monotherapy. All the participants underwent RNFLT imaging with OCT, contrast sensitivity, color discrimination assessment, and perimetry. Results. The average 360° RNFLT of the vigabatrin group was significantly lower when compared to the other groups. The average RNFLT of all quadrants except the temporal one in the vigabatrin group was also significantly reduced. There was no difference in the mean deviation, contrast sensitivity, and color discrimination between the study groups, but they were all significantly lower than the control group. Conclusions. RNFLT measurement with OCT can efficiently identify vigabatrin toxicity in patients with partial symptomatic and cryptogenic epilepsy. Perimetry, contrast sensitivity, and color discrimination assessment might be inconclusive in these particular subgroups of epileptic patients.