Multifocal ERG and full-field ERG in patients on long-term vigabatrin medication.

PURPOSE: To examine the retinal function with different electrophysiological methods in twelve Swedish patients on long-term treatment (2-10 years) with the anti-epileptic drug vigabatrin.

METHODS

Ophthalmological examination of twelve consecutive patients included testing of visual acuity, fundus inspection and fundus photography, kinetic perimetry, full-field ERG and multifocal ERG.

RESULTS

All patients had a visual acuity of 0.7 or better. Fundus inspection revealed no pathology except in one patient who had a pallor of the optic disc. All patients had a normal appearance of the macula. The result of kinetic perimetry was normal in five patients while seven patients had a concentric defect of the visual field. The 30 Hz flicker cone b-wave amplitude in the full-field ERG was abnormal in all of the seven patients with a visual field defect. None of the patients with normal visual fields had a reduction of the 30 Hz flicker cone b-wave amplitude. Six of the twelve patients had a reduced multifocal ERG response but without any correlation with visual field defect.

CONCLUSION

Long-term treatment with vigabatrin seems to selectively reduce retinal cone function. The visual field defects in patients taking vigabatrin correlate with pathology in the full-field ERG (reduction of the cone b-wave amplitude). The results from this study indicate that electroretinography can be used for monitoring patients taking vigabatrin in a more objective manner than with visual field testing.