Relationship Between Alzheimer's Disease and Retinal Choroidal Thickness: A Cross-Sectional Study

The choroid is involved directly or indirectly in many pathological conditions such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS).

The objective of this study was to investigate the association between retinal choroidal properties and the pathology of AD by determining choroidal thickness, hippocampus volume, cognitive functions, and plasma BACE1 activity.

In this cross-sectional study, 37 patients with AD and 34 age-matched controls were included. Retinal choroidal thickness was measured via enhanced depth imaging optical coherence tomography. Hippocampal volume was measured via 3.0T MRI. Cognitive functions were evaluated using the Mini-Mental State Examination (MMSE) and Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-Cog). Plasma BACE1 activity was analyzed using a fluorescence substrate-based plasma assay, and regression model were to analyze the data.

Retinal choroidal thickness was significantly thinner in the AD group than in the control group [(114.81±81.30) μm versus (233.79±38.29) μm, p < 0.05]. Multivariable regression analysis indicated that the ADAS-cog scores (β=-0.772, p = 0.000) and age (β=-0.176, p = 0.015) were independently associated with choroidal thickness. The logistic regression model revealed that the subfoveal choroidal thickness was a significant predictor for AD (OR = 0.984, 95% CI: 0.972-0.997).

There was a general tendency of choroid thinning as the cognitive function declined. Although choroidal thickness was not a potential indicator for early stage AD, it was valuable in monitoring AD progression.