AMYLOID PLAQUES

Two new eye tests in America are being trialled that one day may help doctors to detect the very early stages of Alzheimer’s disease.

Newly released research has revealed that non-invasive retinal testing is now being trialled by scientists in the U.S. that could help flag up the condition by alerting clinicians to the presence of amyloid plaque deposits, a known biological marker of the disease.

Early stage testing could mean that patients are diagnosed or registered as high-risk up to twenty years before noticeable symptoms begin, helping patients get treatment before memory loss develops.

Scientists generally accept that amyloid plaques (a type of residual protein deposit) in the brain are a key marker of the disease.

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Neurologists have believed for a long time that there is a correlation between the amounts of amyloid in the eye and residual protein deposits in the brain. The argument for this correlating factor is a strong one because the retina is formed from the same tissue as the brain when a foetus is developing in the womb.

To confirm this theory, two tests have been developed and trials are currently underway. The tests are known as the Retinal Amyloid Index (by NeuroVision) and the Sapphire II (by Cognoptix).

Ocular based examinations through the years have been used to detect and diagnose Alzheimer’s at any early stage through methods such as optic nerve cupping, pupillary response to tropicamide dilation and ocular muscle movement. However, all have failed to withstand the test of time in terms of sensitivity and specificity.

Professor Keith Black is chairman of the Department of Neurosurgery at Cedars-Sinai Medical Centre in Los Angeles, and co-founder of NeuroVision. He says that if people are going to get Alzheimer’s they begin to develop the hallmarks, such as amyloid deposits, in their 50s.

Professor Black said:

… The key for having an effective treatment for AD is early detection. You want to prevent those brain cells from being killed or dying in the first place.

The Sapphire II test works by measuring the amount of photons (i.e. light particles) captured when scanning the eyes. The amount of photons captured directly correlates with the amount of amyloid in the eye.

Experts state that the Sapphire II is currently in phase one of two in clinical feasibility trials, and that phase three is expected to begin in 2014.

Approximately 800,000 people in Britain suffer from Alzheimer’s and other forms of dementia. The number of cases is predicted to double within a generation.

There is no cure for Alzheimer’s disease and existing drugs can only alleviate symptoms. The condition is diagnosed by memory tests and, in some cases, through brain scans.

Presently, the disease can only be confirmed by a post-mortem examination, which reveals the presence of harmful amyloid plaques in the brain.