O’Bryhim BE, et al. - Authors ascertained if optical coherence tomographic angiography (OCTA) can find early retinal alterations in cognitively normal study participants with preclinical Alzheimer disease (AD) diagnosed by criterion standard biomarker testing. In addition to architectural alterations, retinal microvascular abnormalities were seen in the cognitively healthy individuals with preclinical AD, and these changes happen earlier than previously thought.

Methods

• Experts conducted a case-control study that included 32 participants recruited from the Charles F. and Joanne Knight Alzheimer Disease Research Center, Washington University in St Louis, St Louis, MO.
• Extensive neuropsychometric testing determined that all participants were cognitively normal.
• In order to determine biomarker status, participants underwent positron emission tomography and/or cerebral spinal fluid testing.
• They excluded the individuals with prior ophthalmic disease, media opacity, diabetes, or uncontrolled hypertension.
• They collected the data from July 1, 2016 through September 30, 2017 and analyzed it from July 30, 2016, through December 31, 2017.
• Using an OCTA system from both eyes of all participants, automated measurements of retinal nerve fiber layer thickness, ganglion cell layer thickness, inner and outer foveal thickness, vascular density, macular volume, and foveal avascular zone were collected.
• In order to evaluate individual data outcome, they used separate model III analyses of covariance.

Results

• As per data, 58 eyes from 30 participants (53% female; mean [SD] age, 74.5 [5.6] years; age range, 62-92 years) were included in the analysis.
• Of these, 1 participant was African American and 29 were white.
• Biomarkers positive for AD were seen in 14 participants and thus a diagnosis of preclinical AD (mean [SD] age, 73.5 [4.7] years); 16 without biomarkers served as a control group (mean [SD] age, 75.4 [6.6] years).
• In the biomarker-positive group, the foveal avascular zone was increased compared with controls (mean [SD], 0.364 [0.095] vs 0.275 [0.060] mm²; P=.002).
• In the biomarker-positive group, mean (SD) inner foveal thickness was reduced (66.0 [9.9] vs 75.4 [10.6] μm; P=.03).