Retinal Changes Associated with Alzheimer Disease Confirmed

According to a study published in Acta Neuropathologica, changes in the retina could help predict Alzheimer disease before cognitive symptoms appear. Researchers found increased levels of a specific amyloid beta protein (42 amino acid form of Aβ [Ab42]) in the retinas of those with mild cognitive impairment (MCI) and Alzheimer disease (AD) compared with those with normal cognition (NC). Other notable differences detected in the retina of those with MCI and AD included Aβ accumulation in ganglion cells and a reduced number of microglial cells clearing Aβ, among other results reported. These retinal changes appeared to correspond with reported cognition status and with AD stage.

Researchers performed histologic and biochemical analysis of the retina and brain tissues from 86 postmortem human donors. Donors with premortem clinical diagnoses of MCI and AD were age-matched and sex-matched with donors with NC. The researchers collected 54 retinas from donors with confirmed AD (n=24) or MCI due to AD (n=11) and matched them to donors with NC (n=19). They also analyzed paired brain tissues in a subset of the study (n= 9). For the biochemical analysis, researchers collected eyes from another deceased donor cohort (n = 14) of individuals with confirmed AD (n=7) and NC (n=7). Researchers had access to the participant’s health characteristics and cognitive assessments before death. Participants with diagnoses of macular degeneration, diabetic retinopathy, and glaucoma were excluded from the study. Additional details about the study are available in the published article.

Researchers noted a significant increase in Aβ42 and novel intraneuronal Aβ oligomers (AβOi) in the superior and inferior temporal retinas in participants with MCI and AD when compared to NC participants. In participants with MCI and AD, fewer microglial cells cleared Aβ from the braincompared with NC participants. The accumulation was associated with retinal macrogliosis, microgliosis, and tissue atrophy. The accumulation of Aβ42 was inversely related to cognitive scores after adjustments were made. All of the retinal biomarkers correlated with reported cognitive levels.

According to Maya Koronyo-Hamaoui, PhD, the senior author of this study, “These findings may eventually lead to the development of imaging techniques that allow us to diagnose Alzheimer’s disease earlier and more accurately and monitor its progression noninvasively by looking through the eye.”