O’Bryhim BE, et al. - In this single-center, case-control study, researchers investigated if optical coherence tomographic angiography (OCTA) can detect early retinal alterations in cognitively normal study participants with preclinical Alzheimer disease (AD) diagnosed by criterion standard biomarker testing. According to findings, retinal microvascular abnormalities in addition to architectural alterations were present in cognitively healthy individuals with preclinical AD. These changes were noted to occur at earlier stages of AD than has previously been demonstrated.

Methods

• Researchers performed this case-control study including 32 participants recruited from the Charles F. and Joanne Knight Alzheimer Disease Research Center, Washington University in St Louis, St Louis, MO.
• They used results of extensive neuropsychometric testing to determine cognition in all participants.
• Positron emission tomography and/or cerebral spinal fluid testing were performed on participants to determine biomarker status.
• They excluded individuals with prior ophthalmic disease, media opacity, diabetes, or uncontrolled hypertension.
• From July 1, 2016, through September 30, 2017, they performed data collection, and from July 30, 2016, through December 31, 2017, they performed data analysis.
• Main outcomes and measures included 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 using an OCTA system from both eyes of all participants.
• Individual data outcome was analyzed using separate model III analyses of covariance.

Results

• In this analysis, researchers included 58 eyes from 30 participants (53% female; mean [SD] age, 74.5 [5.6] years; age range, 62-92 years).
• Biomarkers positive for AD were present in 14 participants and, thus, these participants were diagnosed with preclinical AD; 16 without biomarkers served as a control group.
• The biomarker-positive group displayed increased foveal avascular zone vs those in the control group.
• The biomarker-positive group showed decreased mean (SD) inner foveal thickness.