Abstracts

Multiple reports have estimated the incidence, prevalence, risk factors, and functional outcomes associated with the vigabatrin-induced visual field defect (VFD). These studies have yielded a range of prevalence estimates. A recent large study of adults and children with complex partial seizures now helps better define incidence and prevalence and a better understanding of the functional impact of retinal injury., An open-label, multicenter, longitudinal study with blinded perimetric evaluations. Patients were stratified by age and by exposure to vigabatrin (Group 1: currently treated with vigabatrin at study inclusion; Group 2: previously treated with vigabatrin; Group 3: never treated with vigabatrin, but could initiate vigabatrin if visual fields were normal at baseline. Primary outcome was prevalence of bilateral concentric peripheral constriction (BCPC) via perimetry assessment (at least one static and one kinetic). Prevalence was defined as occurrence of BCPC at study inclusion and on first conclusive perimetry examination. Incidence of BCPC was defined as occurrence of BCPC after first dose of vigabatrin and observed on or after study enrollment., At time of submission, a closed database was available on 432 of 563 patients enrolled. Study completion summer of 2006. Patients in Group 1 (48 children; 150 adults) had received vigabatrin for an average of 4 years. Group 2 patients (55 children; 158 adults) received vigabatrin for an average of 1.8 years (children) and 2.5 years (adults) prior to vigabatrin discontinuation. Prevalence rates of BCPC ranged from 6% to 10% in children and from 20% and 30% in adults. Incidence of BCPC was 31% and 44% of children and adults in Group 1, respectively, and 10% and 26% in Group 2. No patients in Group 3 developed BCPC, however only 7 patients received vigabatrin in this group. One subject in Group 3 had definitive findings of BCPC prior to vigabatrin administration. The earliest finding of a VGB-VFD was at 11 months. In general, onset was after 2 years of exposure, with the mean times in this study from first vigabatrin dose to BCPC amongst the six cohorts was from 5 to 7 years (at least one BCPC) and 5.5 to 8.5 years (confirmed BCPC). Blinded scoring of fields in subjects with BCPC showed lateral vision averaged 65 degrees and there was little change on average over approximately 2 years from first to last field examination., The VFD associated with vigabatrin therapy for CPS requires many months to years of treatment to appear, is not progressive, is usually asymptomatic, and can be effectively monitored. Because the onset of efficacy in clinical studies is usually within 12 weeks of initiation, and the earliest onset of the VFD was at 11 months, clinicians have the opportunity to assess efficacy before any substantial risk of field defect exists., (Supported by Ovation Pharmaceuticals, Inc.)