Doctors may one day use eye tests to detect the very early stages of Alzheimer’s disease, according to new research.

Non-invasive retinal testing is now being trialled and could help flag up the condition by alerting doctors to the presence of amyloid plaque deposits, a known marker of the disease.

Testing could mean that patients are diagnosed or are at least flagged up as high-risk up to 20 years before noticeable symptoms begin, helping patients get treatment before memory loss develops.

Experts generally accept that amyloid plaques - a type of protein deposit - in the brain are a key marker of the disease.

Neurologists have also long believed that there is a correlation between the amount of amyloid in the eye and amyloid in the brain.

The arguement for this is strong 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 - the Retinal Amyloid Index by NeuroVision and the Sapphire II by Cognoptix - have been developed and trials are underway, according to a report by Primary Care Optometry News.

Ocular exams through the years have attempted to diagnose Alzheimer’s at an early age,’ Dr Michael Tolentino, a Primary Care Optometry News Editorial Board member, said. The condition is characterised by amyloid plaques in the brain .The condition is characterised by amyloid plaques in the brain

‘We have looked at [various methods of testing, including] optic nerve cupping, pupillary response to tropicamide dilation and ocular muscle movement.

'While all have been investigated, all have failed to withstand the test of time in terms of sensitivity and specificity.'

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

‘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,' he told the journal.

The Sapphire II works by measuring the amount of photons - light 'particles' - captured when scanning the eyes.

The amount of photons captured directly correlates with the amount of amyloid in the eye, explained Carl Sadowsky, medical director of the Premiere Research Institute at Palm Beach Neurology in West Palm Beach, Florida.

He stated 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.

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

There is no cure and existing drugs can only ease symptoms.

The condition is diagnosed by memory tests and occasionally brain scans.

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

Sources:

1. Dailymail:
   Eye tests to detect Alzheimer's.