An examination of the back of the eye, together with an angiography of the vessels of the retina, could help to diagnose Alzheimer’s long before the appearance of clinical symptoms. This is suggested by a study published in the journal JAMA Ophthalmology by researchers from the University of Washington in St. Louis (USA). The researchers showed that these tests, which are easy to perform and minimally invasive, provide results that are similar to those provided by the PET (positron emission tomography) scan or by the collection of cerebrospinal fluid (through a lumbar puncture), carried out in order to check the presence of signs of the illness: in particular, in order to identify beta amyloid plaques (an altered protein) in the brain and the accumulation of tau protein, which are typical of Alzheimer’s.
“In the patients with elevated levels of these proteins (beta amyloid or tau), we detected significant thinning in the centre of the retina,” – explains Rajendra S. Apte, professor of ophthalmology and visual sciences at the University of Washington – “All of us have a small area devoid of blood vessels in the centre of our retinas that is responsible for our most precise vision. However, in people with preclinical Alzheimer’s disease (editor’s note: i.e. those without symptoms) we found that this zone lacking blood vessels was significantly enlarged.” Why does this happen? “The retina and central nervous system are so interconnected”, adds Apte, “that changes in the brain could be reflected in cells in the retina.” The US researchers arrived at these conclusions after examining 30 healthy (or at least seemingly healthy) seventy year olds that took part in two national study projects on ageing. The result was that the PET scan (thanks to special “tracers”), or the collection of cerebrospinal fluid, revealed an increase in the risk of dementia for 17 of them, due to the presence of elevated levels of the proteins amyloid and tau. When they underwent the examination of the back of the eye, and the angiography, these people showed the “signs” of what we are talking about. In the other seventy year olds, on the other hand, all the tests (PET scan, collection of cerebrospinal fluid and eye examination) were within the normal range.
It is clear that the sample is very small – commented the researchers – but the correspondence is enough to justify the performance of broader studies, in an attempt to find cheap and non-invasive examinations that can help to identify those at risk of developing dementia as early as possible. The formation and accumulation of the altered proteins, remember, may start as much as twenty years prior to the appearance of Alzheimer’s, with a loss of memory and cognitive decline. Therefore, it would be important to find an effective and simple way for an early diagnosis. The illness is still very difficult to treat, but many previously unknown aspects have been clarified in recent decades, and the search for effective therapies is continuing at an intensive pace.