Vigabatrin-associated visual field defects in children

Purpose Vigabatrin (Sabril), a drug that blocks GABA transaminase, has been used in the treatment of epilepsy since 1989. There have been reports of i rreversible constriction of the visual field in adult patients related to v igabatrin (VGB) therapy, resulting in reduced VGB usage in adults. Although used as a second or third line agent in adults, in children it is often co nsidered as a first line treatment for several subgroups of seizures in spi te of there being no way, in the majority of cases, to monitor visual field s. Some of these children have a pre-existing visual field defect as part o f their primary disorder. We aimed to identify whether visual field loss du e to VGB was occurring in our hospital. Methods We have studied the results of ophthalmic examination in 14 childre n on VGB at Great Ormond Street Hospital who were able to perform Goldmann visual fields. Results Ten of the 14 patients had constriction of their visual fields attr ibuted to VGB. In addition there were 2 patients with suspicious visual fie ld defects thought to be due to VGB. There was pre-existing visual pathway damage in 4 cases and in 2 of these optic disc pallor increased in associat ion with constricted visual fields. However, the optic discs were normal in 7 patients in spite of visual field constriction. Visual acuity tvas gener ally normal in spite of gross visual field constriction. Conclusions We believe that VGB should be used with great caution where the re is preexisting visual pathway damage. In other cases the benefits should be considered in relation to the risks, which include irreversible visual field damage. At present visual fields can only be monitored by perimetry, which is often not possible in children with epilepsy.