Guideline for prescribing vigabatrin in children has been revised

EDITOR—In 1998 a paediatric advisory group in the United Kingdom produced a guideline to help clinicians when prescribing vigabatrin in children.1 The visual field defect reported in association with the drug 2 has now been confirmed in five children treated with it. The paediatric guideline has now been revised and replaced with the one below, which reflects the current opinion of the advisory group.

• The defect is specific—a bilateral and concentric constriction that, within a 30° radius from fixation, consists of a nasal loss extending in an annulus over the horizontal midline, with a relative sparing of the temporal field. Its pathogenesis is thought to involve cone and amacrine cell dysfunction in the retina. The prevalence in adults is about 30% 3 …