Macular pigment, visual function, and macular disease among subjects with Alzheimer's disease: an exploratory study

Abstract

Background: The macula (central retina) contains a yellow pigment, comprising the dietary carotenoids lutein (L), zeaxanthin (Z), and meso-zeaxanthin, known as macular pigment (MP). The concentrations of MP's constituent carotenoids in retina and brain tissue correlate, and there is a biologically-plausible rationale, supported by emerging evidence, that MP's constituent carotenoids are also important for cognitive function.

Objective: To investigate if patients with Alzheimer's disease (AD) are comparable to controls in terms of MP and visual function.

Methods: 36 patients with moderate AD and 33 controls with the same age range participated. MP was measured using dual-wavelength autofluorescence (Heidelberg Spectralis®); cognitive function was assessed using a battery of cognition tests (including Cambridge Neuropsychological Test Automated Battery). Visual function was recorded by measuring best corrected visual acuity (BCVA) and contrast sensitivity (CS). Serum L and Z concentrations (by HPLC) and age-related macular degeneration (AMD, by retinal examination) status were also assessed.

Results: In the AD group, central MP (i.e., at 0.23°) and MP volume were significantly lower than the control group (p < 0.001 for both), as were measures of BCVA, CS, and serum L and Z concentrations (p < 0.05, for all).

Conclusion: AD patients were observed to exhibit significantly less MP, lower serum concentrations of L and Z, poorer vision, and a higher occurrence of AMD when compared to control subjects. A clinical trial in AD patients designed to investigate the impact of macular carotenoid supplementation with respect to MP, visual function, and cognitive function is merited.

Keywords: Age-related macular degeneration; Alzheimer's disease; cognitive function; contrast sensitivity; lutein; meso-zeaxanthin; visual function; zeaxanthin.