Extract

Since Eke et al's report of persistent visual field constriction associated with vigabatrin, several letters have been published in the BMJ, including that by Mackenzie and Klistomer, that draw attention to the occurrence of visual field changes in asymptomatic patients as well as those with symptoms.

A prescription-event monitoring study of vigabatrin conducted between 1991 and 1994 identified four cases of bilateral, persistent visual field defect for which there was objective evidence and no alternative cause given.  The study cohort consisted of 10,033 living patients for whom questionnaires containing clinical information were returned.  The mean duration of treatment for these four cases was 19.8 months; for the total cohort it was 14.2 months.  Subsequently, we were informed of another seven patients in this cohort in whom visual field defect had been reported after the end of the study's observation period.  This suggested that further cases might be identified if the period of observation was extended.