The Alzheimer’s disease is the most common type of dementia worldwide with no cure or treatment. It can severely disrupt the life of the patient and caregivers and is both emotionally and physically challenging for caregivers. There are millions living with Alzheimer’s across the globe. With an aging population, the incidence is expected to increase significantly in the coming decades. Current tools for diagnosis rely on clinical exam and symptoms, invasive tests such as evaluating the cerebrospinal fluid using lumbar puncture or expensive neuro-imaging such as MRI or PET scans of the brain. There are as yet not accurate, rapid, cost-effective, easy to use and non-invasive tools for early diagnosis of Alzheimer’s.
Eyes don’t lie
A study of more than 200 subjects at Duke Eye Centre, Duke University, North Carolina, USA, published in the journal Ophthalmology Retina, suggests that the loss of blood vessels in the retina could signal Alzheimer’s. The study included results of eye tests of 39 persons with Alzheimer’s. It found that the web of capillaries in the superficial layer of the retina was less dense and even sparse in places compared to similarly aged healthy people. The changes were also seen in subjects with mild cognitive impairment which is often a precursor to Alzheimer’s. These differences in blood-vessel density were statistically significant even after the researchers controlled for factors, including age, sex, and education. The Duke research team was led by Dr Dilraj S Grewal, a doctor of Indian origin, a Duke ophthalmologist, retinal surgeon and a lead author on the study. The team also studied other changes in the retina that could signal trouble in the brain, such as thinning of some of the retinal nerve layers.
Non-invasive diagnostic tool
These small blood vessels in the back of eye cannot be seen during a regular eye exam and were evaluated using a new non-invasive technology, OCT-Angiography, that is a dye-free angiography of the retina. It takes high-resolution images of very small blood vessels within the retina. It is possible that these changes in blood vessel density in the retina mirror what’s going on in the tiny blood vessels in the brain (the ones that could earlier be seen only under a microscope), perhaps even before the doctors are able to detect any changes in cognition or mental status or before changes show up on brain scans such as an MRI or cerebral angiogram, which highlight only larger blood vessels.
