Tangent screens are still useful in the assessment of vigabatrin induced visual field defects
- The Eye Clinic, Aberdeen Royal Infirmary, Forester Hill, Aberdeen
- Correspondence to: Dr Olson; j.olson{at}arh.grampian.scot.nhs.uk
- Accepted 13 February 2002
Vigabatrin induced constriction of peripheral visual fields was first reported in 1997.1 The potential mechanisms of vigabatrin induced peripheral field constriction are many,2 but in our opinion, not enough attention has been paid to the method and appropriateness of recording this constriction. Current recommendations for patients prescribed vigabatrin are that they are screened at regular intervals by automated perimetry. Automated perimetry cannot, however, differentiate between pathological and functional (non-physiological) constriction of the visual field. Furthermore, automated perimetry, although deceptively simple for the operator to perform, is notoriously laborious and fatiguing for the patient. Although several safeguards are built into automated perimetry, in the form of reliability indices, there are traps for the unwary. This is clearly demonstrated in the …
