Vigabatrin

Control

Vigabatrin

First order kernel

Second order kernel

1 nV/deg2

10ms

Fig. 6. Average of all 61 traces from a 59-year-old control subject (dashed lines) and a 53-year-old patient with a mild visual field constriction who had been taking vigabatrin for 5 years (continuous lines). The first-order kernel is shown in the upper traces and the second-order kernel in the lower. Potentials are delayed and in most cases reduced in the vigabatrin patient.

cases for which the alterations appear to affect all retinal areas and all potentials more or less equally.

Vigabatrin Treatment

Vigabatrin is an effective antiepileptic drug that inhibits GABA aminotransferase, an enzyme inducing degradation of GABA in the retina and brain, but it has been reported as causing visual disturbances [35]. In the course of a study to assess the visual alterations caused by vigabatrin, mfOPs were recorded from 20 patients and compared to those of control subjects [36].

In Fig. 6 we show representative average traces of all 61 hexagons from a 59-year-old control subject along with those of a 53-year-old patient who had been taking vigabatrin for 5 years and who manifested a mild visual field constriction. All potentials of both firstand second-order kernel are delayed by about 2–3 ms. Since such abnormalities of the mfOPs were seen in all patients with visual field defects, a dysfunction of GABAergic retinal cell transmission might be assumed to contribute to the increased implicit time.