AIM: We investigated the peripapillary retinal nerve fiber layer thickness with optical coherence tomography in epileptic children receiving valproic acid monotherapy. MATERIALS AND METHODS: The study was conducted on children aged 8-16 years who were undergoing valproic acid monotherapy for epilepsy. The study group comprised a total of 40 children who met the inclusion criteria and 40 healthy age- and sex-matched children as a control group. Children with at least a 1-year history of epilepsy and taking 10-40 mg/kg/day treatment were included in the study. Peripapillary retinal nerve fiber layer thickness measurements were performed using Cirrus HD optical coherence tomography. All children and parents were informed about the study and informed consent was obtained from the parents of all the participants. RESULTS: The study group included 21 girls and 19 boys with a mean age of 10.6 +/- 2.3 years. According to the results of optical coherence tomography measurements, the mean peripapillary retinal nerve fiber layer thickness was 91.6 +/- 9.7 in the patient group and 95.5 +/- 7.4 mu m in the control group (P < 0.05). The superior peripapillary retinal nerve fiber layer thickness was 112.0 +/- 13.2 in the patient group and 120.0 +/- 14.7 mu m in the control group (P < 0.02). According to the results of both measurements, the peripapillary retinal nerve fiber layer thickness was significantly lower in the patient group. Neither color vision loss nor visual field examination abnormality could be documented. CONCLUSION: According to the optical coherence tomography measurements, the average and superior peripapillary retinal nerve fiber layer thicknesses were thinner in patients with epilepsy who were receiving valproic acid monotherapy compared with healthy children. This situation can lead to undesirable results in terms of eye health. New studies are needed to investigate whether these findings are the result of epilepsy or can be attributed to valproic acid and whether there are adverse effects of valproic acid later in life.