INCOMPLETE ACHROMATOPSIA IN ALZHEIMERS-DISEASE

We report that patients with Alzheimer's disease (AD) have a selective deficit in blue hue discrimination, as assessed with three clinical m easures of color vision. The Farnsworth D-15 Test, the Lanthony New Co lor Test, and the City University Color Vision Test were administered to 32 patients with AD (ranging in dementia severity from mild to seve re) and 32 age-matched normal control subjects (NCS). Of the AD patien ts, 11 who were representative of the larger group for age, education level, and dementia severity received a complete neuro-ophthalmologica l examination that ruled out obvious disorders of the anterior visual structures. AD patients made significantly more tritan (blue) errors t han NCS on all three color vision tests but did not make more protan ( red) or deutan (green) errors on two of the three tests. The results s upport the conclusion that there is a deficit in color discrimination in AD that is specific to blue hues, and oppose the hypothesis that AD does not deleteriously affect the color-opponent visual channel. In t he absence of obvious damage to anterior visual structures, the likely substrates for the observed deficit are peristriate and inferotempora l visual cortices, which are subject to significant neuropathology in AD.