Although a highly effective medication for treatment of infantile spasms and refractory complex partial seizures, vigabatrin (VGB) (Sabril) has been limited in its use because of reports of bilaterally constricted visual fields and one report of decreased central visual acuity. The incidence, prevalence, onset and prognosis of these visual deficits remain unknown. Despite this potentially serious visual issue, VGB was approved by the US FDA contingent upon careful monitoring with a risk evaluation mitigation strategy program. The risk evaluation mitigation strategy program has functioned well, enrolling patients in the USA who are eligible for treatment. The baseline data has yielded the new and surprising finding that 23% of 928 patients who were able to perform reliable visual testing at baseline demonstrated abnormalities. This finding was considered ‘surprising’ since there was a tacit assumption that patients eligible for VGB therapy had a normal visual system as a baseline. Also, somewhat perplexing is the relatively low number of patients who have visual findings possibly or probably attributable to VGB. The results from the ongoing, open-label ‘vision study’ will provide the first prospective, reading-centered controlled data about VGB and visual function. The results of this study will further define the benefit/risk profile of this product and its future use over the next 5 years.