Alzheimer's disease, one of the main causes of dementia, is a neurodegenerative disease that progressively leads to a decline in brain and cognitive functions, as well as to a reduction in the quality of life of the sufferer and, consequently, of his or her family. The diagnosis of Alzheimer's is still complexThis is because, to date, there is no test that leads to a certain diagnosis, except by autopsy, i.e. only after the death of the subject. Moreover, the numerous tests required to the living patient for diagnostic certainty are expensive, invasive and require very long clinical evaluation times.
According to a recent study, a new hope appears to come from an examination analysing the ocular blood vessels. In fact, it has been observed that In Alzheimer's patients, there is a change at the microvascular level of the retina that consists of a remarkable reduction in the number of capillary vessels and perfusion densityas well as a decrease in thickness of ganglion cells, a type by retinal nerve cells. The authors hypothesised, therefore, that changes in the eye may reflect the changes that occur in the brain nervous system following the onset of Alzheimer's.
These microvascular changes are detectable by means of a modern technique, angiography based on optical coherence tomography (angio-OCT or OCTA), which allows rapid and non-invasive visualisation of the vasculature and optic nerve with a detailed three-dimensional reconstruction. OCTA uses the signal caused by the movement of red blood cells in the retinal capillaries, detected by non-visible light waves, to acquire high-resolution images of the different layers of the eye. Moreover, OCTA does not include the side effects related to the injection of dyes or contrast media.
This technique is also specific as it is able to detect microvascular differences between dementia caused by Alzheimer's disease and mild cognitive impairment, an early stage of dementia considered a risk factor for progression to Alzheimer's disease.
THE OCTA, therefore, could constitute a useful, non-invasive and low-cost screening tool for diagnosing the disease at an early stage in which the symptomatology is not yet evident.
Sources
-Retinal microvascular and neurodegenerative changes in Alzheimer's Disease and Mild Cognitive Impairment compared with control participants. Yoon S. P. et al. 2019; Ophthalmol Retina, in press. https://doi.org/10.1016/j.oret.2019.02.002
-Current understanding of Alzheimer's disease diagnosis and treatment. Weller J., Budson A. 2018; F1000Research 7:1161. https://doi.org/10.12688/f1000research.14506.1
-Optical coherence tomography angiography: A comprehensive review of current methods and clinical applications. Kashani A. H. et al. 2017; Prog Retin Eye Res60:66-100
Dr. Carmelo Chines
Direttore responsabile