Abstract

Alzheimer’s disease (AD) is characterized by maximal degeneration of the parietal and temporal lobes with relative sparing of primary visual areas. As may be expected from this pattern of degeneration, AD patients as a group are widely impaired on tests of higher-order visuospatial function, whereas only a minority show deficiencies in color vision, Vernier acuity, and stereoacuity. This pattern of functional sparing of basic visual processes does not hold, however, for contrast sensitivity function, which is commonly impaired at all spatial frequencies in patients with AD, relative to age-matched controls.¹ In cats, ablation of the striate cortex results in only modest changes in contrast sensitivity function; furthermore, blocking the ON channel in the monkey retina affects contrast sensitivity but not color discrimination, acuity, motion detection or stereopsis. Thus contrast sensitivity, unlike the other basic visual functions we have measured in AD, may involve precortical brain areas. In light of a recent report of optic nerve degeneration and retinal changes in AD,² these observations raise the intriguing possibility that, as far as basic visual processes are concerned, AD is a precortical, not a cortical disease.

© 1986 Optical Society of America