Vigabatrin effect on inner retinal function

Objective: To determine the degree of electroretinal dysfunction in a group of patients taking Vigabatrin (VGB). Additionally, to investigate the role of cumulative dosage, the role of VGB alone or in combination with other a nticonvulsants, and whether recent discontinuance of VGB affects electroret inal function as measured by the electroretinogram (ERG). Design: Retrospective, comparative case series. Participants: Forty patients (18 male, 22 female) with a mean age of 35 yea rs were studied as three groups: the VGB multitherapy group (n = 24) includ ed those taking VGB with other anticonvulsants, the VGB monotherapy group ( n = 9) included those taking VGB alone, and the off-VGB group (n = 7) inclu ded those who had discontinued VGB in the last 6 months. Methods, Scotopic flash, photopic flash, and 30-Hz flicker ERG results were recorded according to the International Society for Clinical Electrophysio logy of Vision (ISCEV) standard. The clinical electro-oculogram (EOG) resul ts were recorded according to the ISCEV standard. Main Outcome Measures: Implicit time and amplitudes of the A- and B-waves o f the flash and 30-Hz flicker ERGs were recorded. Summed amplitude of the f irst three oscillatory potential wavelets were recorded. The light-peak to- dark-trough Arden ratio of the EOG was evaluated. Results: Although photopic ERG B-wave reduction was most frequent in patien ts in the VGB multitherapy group (48% of eyes), a significant number of eye s in all three groups had scotopic ERG B-wave reduction. The 30-Hz flicker ERG result was abnormally reduced in all three groups. There was no signifi cant difference in the frequency of occurrence in ERG result abnormalities between the VGB monotherapy and VGB multitherapy groups. The EOG results re vealed reduced Arden ratios in all three groups; however, there was a signi ficantly lower frequency of EOG abnormalities noted in the off-VGB group (P = 0.0373). There was no statistically significant relationship between the frequency of electrodiagnostic abnormalities and the duration of use or th e total cumulative dosage of Vigabatrin in any of the three groups. Conclusions: These findings of scotopic ERG result abnormalities suggest th at VGB alone has an effect on inner electroretinal function at the level of the Muller cell. Concomitant EOG abnormalities suggest a substantial effec t of VGB on outer retinal function that may be reversible after cessation o f VGB treatment. Ophthalmology 2001;108:1493-1498 (C) 2001 by the American Academy of Ophthalmology.