Vigabatrin and retinal changes.

PURPOSE: Vigabatrin is an effective antiepileptic drug but visual field constriction (VFC) is found to be a severe side-effect. The aims have been to investigate whether visual field constriction (VFC) is related to changes in the electroretinography (ERG).
METHODS: Twenty patients with localisations related epilepsy of whom one half had received vigabatrin were subjected to examination without informing about the treatment given. The eye examination included Goldmann perimetry and ERG.
RESULTS: All the patients had normal visual acuity. A total of three patients (30%) in the vigabatrin group and none in the control group were found to have VFC. In the vigabatrin group ERG examination were normal in one case, in five cases there were changes scotopic, photopic and in the oscillatory potentials (OP), while the remaining four had changes in two of these parameters. OPs were abnormal in eight of 10 patients. Of the three patients with VFC all had changes in ERG. The four patients with the most severe abnormalities in ERG had received high daily doses of vigabatrin (4 - 6 mg) in a period. In the control group no abnormality was observed in five cases, and in the remaining five changes were present in one or two of the potentials.
CONCLUSION: It is found that 30% of patients treated with vigabatrin, develop VFC, and none in the control group. Similarly more patients in the vigabatrin group had changes in the ERG as compared to the control group, and the number of abnormal potentials are significantly higher among patients with VFC compared to those without. But the finding of abnormal ERG results is not synonymous with VFC, and this is important to bear in mind when examining patients that cannot cooperate to a VF examination. An individual sensitivity to vigabatrin is supposed, but severe ERG changes occurred in all patients having had high daily doses > or = 4 g.