Purpose
To evaluate color vision changes and retinal processing of chromatic and luminance pathways in subjects with Alzheimer disease (AD) and mild cognitive impairment (MCI) compared with a matched control group and whether such changes are associated with impaired brain glucose metabolism and β-amyloid deposition in the brain.
Methods
We evaluated 13 patients with AD (72.4 ± 7.7 years), 23 patients with MCI (72.5 ± 5.5 years), and 18 controls of comparable age (
P
= 0.44) using Cambridge color test and the heterochromatic flicker ERG (HF-ERG). The Cambridge color test was performed using the trivector protocol to estimate the protan, deutan and tritan color confusion axes. HF-ERG responses were measured at a frequency of 12 Hz, which ERGs reflect chromatic activity, and at 36 Hz, reflecting luminance pathway. A study subsample was performed using neuropsychological assessments and positron emission tomography.
Results
Patients with AD presented higher mean values indicating poorer color discrimination for protan (
P
= 0.04) and deutan (
P
= 0.001) axes compared with the controls. Along the tritan axis, both patients with AD and patients with MCI showed decreased color vision (
P
= 0.001 and
P
= 0.001) compared with controls. The analyses from the HF-ERG protocol revealed no differences between the groups (
P
= 0.31 and
P
= 0.41). Diffuse color vision loss was found in individuals with signs of neurodegeneration (protan
P
= 0.002, deutan
P
= 0.003 and tritan
P
= 0.01), but not in individuals with signs of β-amyloid deposition only (protan
P
= 0.39, deutan
P
= 0.48, tritan
P
= 0.63), regardless of their clinical classification.
Conclusions
Here, patients with AD and patients with MCI present acquired color vision deficiency that may be linked with impaired brain metabolism.