Abstract
Quantitative perimetric studies in two patients with involvement of a lateral geniculate nucleus (caused by astrocytoma in one and a small arteriovenous malformation in the other) revealed strikingly incongruous defects in the contralateral homonymous fields of vision. The patterns of these hemianopias were analysed and correlated anatomically in terms of established patterns of retinal projections within the six cellular laminae of the geniculate nucleus. Incongruous wedge-shaped field defects recorded in the patient with the astrocytoma are unique and appear to be pathognomonic of focal geniculate disease in the dorsal crest of the nucleus.