Visual prognostic value of the pattern electroretinogram in chiasmal compression

Background/aims-The visual loss associated with compression of the optic ch iasm by pituitary tumours may be transient or permanent, possibly related t o the extent of irreversible retrograde degeneration to the retinal ganglio n cells. The pattern electroretinogram (PERG) N95 component is thought to r ise in relation to retinal ganglion cell function and hence may be a potent ial prognostic indicator for visual function following decompressive surger y. Methods-The notes and electrodiagnostic records of 72 eyes from 36 patients with chiasmal compression were retrospectively analysed. Results-The postoperative change in visual held was found to be associated with the PERG N95:P50 ratio (p=0.01). Improvement in visual field was shown by a greater proportion of eyes with a normal N95:P50 ratio (65%) than wit h an abnormal ratio (27%). No change in visual field occurred in 26% of the eyes with a normal N95:P50 ratio compared with 67% of those with an abnorm al ratio. Only 8% of eyes showed a worsening of visual field following surg ery, in similar proportions for eyes with normal and abnormal N95:P50 ratio s. There was no significant relationship with visual acuity. Conclusion The PERG is a useful visual prognostic indicator in the preopera tive assessment of chiasmal compression.