Prevalence of visual field loss following exposure to vigabatrin therapy: A systematic review

P>Purpose: Vigabatrin is an efficacious antiepileptic drug licensed as add-on therapy in refractory epilepsy and used in infantile spasms. Eight years after licensing, there emerged a strong and possibly causative association with bilateral visual field loss. We report a systematic review ascertaining the magnitude of risk of vigabatrin associated visual field loss (VAVFL) and any clinical predictors of risk. Methods: Electronic searches, including MEDLINE (1966-2009), EMBASE (1974-2009), and CINAHL (1982-2009), were conducted. Reports, published in full, of observational studies investigating the prevalence of visual field loss in patients with partial epilepsy treated with vigabatrin were included. Outcomes were the proportion with visual field loss, and the relative risk of VAVFL compared to similar nonexposed patients with epilepsy. Key Findings: Thirty-two studies were identified, which included 1,678 patients exposed to vigabatrin and 406 controls. Of the 1,678 exposed patients, 738 (44%) had visual field loss compared to just 30 (7%) among the 406 controls. The random-effects estimate for the proportion of adults with visual field loss was 52% [95% confidence interval (CI) 46-59]. The estimate for children was lower at 34% (95% CI 25-42). The relative risk for field loss in vigabatrin-exposed patients was 4.0 (95% CI 2.9-5.5). Larger mean cumulative dose of vigabatrin and increasing age were associated with a higher proportion of patients with visual field loss. Significance: Vigabatrin should be reserved for patients with epilepsy for whom there is no other alternative or for patients who have determined the benefit of ongoing treatment to outweigh the risk of VAVFL.