Efficacy of Oral Valproic Acid in Patients with Retinitis Pigmentosa

Purpose: To evaluate the efficacy of valproic acid (VPA) on visual function in patients with retinitis pigmentosa (RP). Methods: Thirty patients (60 eyes) with typical RP were recruited for the study. Of these, 15 patients received oral VPA (500 mg once daily) for a period of 1 year (group 1) and the remaining 15 received no treatment (group 2) and served as controls. The effect of VPA on visual function was determined in terms of visual acuity, amplitude and implicit time in multifocal electroretinography (mfERG), and visual evoked response (VER) performed at presentation and at the third month, sixth month, and 1 year in both groups. Side effects of oral VPA were also monitored. Results: At 1-year follow-up, 14 of 15 patients in group 1 had improvement in median best corrected visual acuity (BCVA) from 1.8 [Range (R) 1-3] at baseline to 1.3 (R, 0.6-1.3) (P < 0.001). In contrast, there was a slight decrease in median BCVA from 1.8 (0.8-3) logarithm of the minimum angle of resolution (logMAR) at baseline to 1.83 (P = 0.3) in the control arm. There was also a statistically significant increase in improvement in amplitude and latency/implicit time in mfERG and VER in this group (P < 0.001). However, no such improvement was observed in the control arm. Conclusions: Thus, VPA seems to have a positive effect on the visual functions in RP patients. Long-term studies evaluating the dose modifications, genetic analysis, and change in visual fields will add to our current knowledge.