Valproic acid's effects on visual acuity in retinitis pigmentosa: a systemic review and Meta-analysis

To gain a better understanding of the overall efficacy of valproic acid (VPA) treatment for retinitis pigmentosa (RP).

Publications in PubMed, EMBASE, Cochrane Library, Web of Science and Clinicaltrials.gov were searched for clinical trials of patients with RP assigned to treatment with VPA. Patients' pre- and post-treatment visual field (VF) and best-corrected visual acuity (BCVA) scores were extracted and compared to assess changes.

A total of 78 reports were retrieved and 6 studies involving 116 patients were included in the Meta-analysis. The combined results showed a significant decrease in logarithm of minimal angle of resolution (logMAR) scores, calculated using baseline and post-treatment BCVA (P<0.00001, mean difference=-0.05, 95%CI: -0.05, -0.04, I ²=36%) scores, which means there was considerable improvement in visual acuity. Meanwhile, more BCVA changes were observed in short-term (≤6mo) treatment studies (P<0.00001, mean difference=-0.05, 95%CI: -0.05, -0.04, I ²=38%), studies conducted in Asia (P<0.00001, mean difference=-0.05, 95%CI: -0.05, -0.04, I ²=4%), studies with a sample size of 30 or fewer patients (P<0.00001, mean difference=-0.05, 95%CI: -0.05, -0.04, I ²=38%) and prospective studies (P<0.00001, mean difference=-0.05, 95%CI: -0.05, -0.04, I ²=0%). However, VPA's effect on VF was inconsistent across studies (P=0.75, mean difference=-22.76, 95%CI: -160.56, 115.05, I ²=68%).

This Meta-analysis reveals that most RP patients who were treated with VPA showed improvement in BCVA. However, its effect on VF remains inconsistent. VPA may be a promising treatment for RP.