Diagnosis of Alzheimer’s Disease by Assessing Structural and Microvasculature Changes in the Retina Using Optical Coherence Tomography Angiography – a Review of Eye Biomarkers for Alzheimer’s Disease

Alzheimer’s disease is a chronic neurodegenerative disorder that manifests as cognitive decline and memory impairment. Diagnosis is

mainly based on the assessment of cognitive functions, while neuroimaging techniques are still very expensive and difficult to access.

During the embryogenesis phase, the retina and optic nerve develop as a direct extension of the diencephalon, so that abnormalities

occurring in the brain can also be observed in the fundus of the eye. Using optical coherence tomography, a significant decrease in

thickness of the retinal nerve fiber layer and a reduction in retinal thickness and volume in the macular area have been demonstrated.

In post-mortem studies of patients with Alzheimer’s disease, it has been proven that the disease, in addition to nerve cell damage,

also has its cerebrovascular pathology. A potential association with the accumulation of abnormal Aβ around vascular walls, impaired

blood flow and the diameter of the vessels in the retina have been identified in patients with AD. Using optical coherence tomography

angiography to retinal microcirculation imaging showed a reduction in retinal vascular density compared to the control group. Unfortunately,

the structural changes in the retina in patients with dementia observed by means of optical coherence tomography images

may be non-specific and common to other neurodegenerative diseases, such as reduction in the thickness of the retinal nerve fiber

layer in glaucoma. Nevertheless, combined measurements of retinal structural changes and microvasculature assessment in each

retinal plexuses using optical coherence tomography angiography potentially increase the diagnostic ability of Alzheimer’s disease.