Toxic effect of vigabatrin on retinal nerve fiber layer

Purpose To investigate whether peripheral and central visual field defects detected among epilepsy patients treated with vigabatrin are associated with reduced peripapillary retinal nerve fiber layer thickness as measured with optic coherence tomography (OCT). Methods Nine epilepsy patients with vigabatrin-attributed visual field loss (group 1) and seven patients(age and sex matched) with epilepsy treated with other drugs(control group 2) were regularly examined with automated perimetry up to 60 degrees from fixation point (Humphrey Field Analyser). Peripapillary retinal nerve fiber layer thickness (RNFLT) was quantified by optic coherence tomography (OCT) using Fast RNFLT protocol, Stratus OCT (3.0). Five of the patients in group 1 had peripheral visual field defects, (group 1a), four had a central field defect(group 1b). All patients in control group 2 had normal visual field. Results Patients with vigabatrin-attributed visual field loss had attenuated total RNFLT compared to controls (right eye : mean total RNFLT: group 1: 75.6 µm (SD 12.7); group 2: 103.5 µm (SD 9.7), mean difference 27.9 µm (CI 15.9-39.9;P < 0.001). The nasal and inferior sectors RNFLT were more attenuated in patients with vigabatrin-attributed visual field loss compared to controls, while no difference was detected in the temporal RNFLT. Both individuals with peripheral and central visual field losses had attenuated mean total RNFLT compared to controls (P = 0.006 and P= 0.002, respectively). Conclusion Vigabatrin-attributed visual field defects are associated with reduced RNFLT. Combination of perimetry and OCT can efficiently detect vigabatrin induced retinal nerve fiber damage.