[Vision in Alzheimer's disease].

Disturbances of visual function can be the first symptom of Alzheimer disease (AD). Several cases of pathologically proven AD associated with Balint's syndrome have been reported, and, in most of them, an unusual occipito-parietal predominance of neurofibrillary tangles (NFT) and neuritic plaques (NP) was found. Systematic assessment of visual functions in groups of patients presenting with dementia of Alzheimer type (DAT) have shown deficits in several tests, especially in stereo-acuity, in motion sensitivity, in contrast sensitivity for low spatial frequencies and in backward masking sensitivity. In electrophysiological studies, abnormalities of flash visual evoked potentials, contrasting with preservation of pattern visual evoked potentials, have been repeatedly reported. Moreover, decreased glucose metabolism in visual association cortex and in partietal cortex is frequent in DAT. Quantitative studies of regional distribution of NFT and NP in AD indicate constant involvement of associative visual cortex and preservation of primary visual cortex. All these findings, taken together, suggest that the occipito-parietal cortex which constitutes the dorsal visual system and subtends visuo-spatial functions, is selectively affected in AD.