[Vigabatrin and visual field defects. A Danish material with evaluation of different screening methods]

The aim of the study was to assess the prevalence of visual field constriction in a consecutive, unselected series of patients in the Copenhagen area treated with vigabatrin for severe epilepsy, and further to assess appropriate screening techniques for detecting such visual field defects.

During 1999, 36 vigabatrin-treated patients (aged 13-67) referred to the eye clinic, had a full ophthalmic examination. Routine visual field testing by means of a) finger movements and b) a tangent screen was supplemented by c) manual kinetic Goldmann perimetry and d) automated static threshold profile perimetry (Octopus).

Of the 31 subjects accepted for entry, 80% showed some degree of visual field constriction. The affection was regarded as slight in 15 cases, moderate in seven, and severe in four. Both kinetic Goldmann and static computerised perimetry disclosed the peripheral defects in those affected. By Goldmann perimetry, it appeared as a smooth narrowing of outer visual field borders, whereas Octopus demonstrated a less regular, more scattered loss of sensitivity.

Eighty per cent with peripheral field affection is among the highest reported frequencies in a vigabatrin-treated series of patients so far. An association with a cumulated dose of the drug was demonstrated. Visual field testing by finger movements and tangent screen evaluation will not reveal the initial peripheral losses of the visual field. For this purpose, we found manual kinetic Goldmann perimetry a valid alternative to modern computerised perimetric techniques. Goldmann takes less time, makes the co-operation of the patient easier, and the interpretation is simple.