An Alzheimer’s disease diagnosis often depends on symptoms more than physical signs, but some structural changes can help identify the disease.1 Usually, these signs require the use of magnetic resonance imaging, but a team of researchers are now showing that ocular imaging with optical coherence tomography angiography (OCT-A) can contribute valuable data.1,2 The technology is capable of revealing significant decline in parafoveal flow and vessel density in patients who show early cognitive impairment related to Alzheimer’s, providing clinicians with a potential early disease biomarker.2
Until the advent of OCT-A, large vascular channels in the peripapillary region often obscured the subtle capillary changes that may help identify early Alzheimer’s, the report states.2
The Chicago-based research team conducted a single-center study of 32 participants. Patients both with early Alzheimer’s disease or amnestic type mild cognitive impairment were evaluated using OCT-A imaging and compared with healthy controls.2 The imaging focused on their parafoveal superficial capillary plexus (SCP) and two vascular layers in the peripapillary region—the radial peripapillary capillary and superficial vascular complex. The team measured the vascular density, vessel length density, adjusted flow index (AFI) and structural retinal nerve fiber layer thickness in all the subjects.2 Those parameters were all compared with the subjects’ cognitive performance on the Montreal Cognitive Assessment (MoCA).
They discovered that patients who already showed cognitive impairment had statistically significant decreases in parafoveal SCP vessel density and adjusted flow index compared with the control group. No statistically significant difference was observed in peripapillary parameters. Researchers noted a significant positive correlation between MoCA scores for the entire study cohort and both the parafoveal SCP vessel density and radial peripapillary capillary vessel length density.2
The investigators speculate that this non-invasive approach’s ability to detect early capillary changes could one day help predict Alzheimer’s.2
1. Mayo Clinic. Diagnosing Alzheimer’s: how Alzheimer’s is diagnosed. www.mayoclinic.org/diseases-conditions/alzheimers-disease/in-depth/alzheimers/art-20048075. October 13, 2016. Accessed April 15, 2019.
2. Zhang Y, Zhou N, Knoll B, et al. Parafoveal vessel loss and correlation between peripapillary vessel density and cognitive performance in amnestic mild cognitive impairment and early Alzheimer’s disease on optical coherence tomography angiography. journals.plos.org/plosone/article?id=10.1371/journal.pone.0214685. April 2, 2019. Accessed April 15, 2019.