One step closer to eye tests to reveal early signs of memory problems and dementia

Thinning of the retinal nerve and protein deposits in the eye could be used to detect early signs of neurodegeneration.

This is according to new research presented today (Tuesday 26 July) at Alzheimer’s Association International Conference (AAIC) 2016 in Toronto.

Researchers at Moorfields Eye Hospital in London conducted a type of eye scan called spectral domain optical coherence tomography (SD-OCT) in 33,068 people aged 40–69. They measured the thickness of the retinal nerve fibre layer (RNFL), which is known to decrease with age. Participants also took part in tests of memory, reasoning, and reaction time.

A thinner retinal nerve fibre layer was strongly correlated with poorer performance on any one of the cognitive tests, as well as with the number of tests failed overall. For each additional test failed, the RFNL was thinner by 1 micrometre.

Amyloid protein, which builds up in the brains of people with Alzheimer’s disease, is known to accumulate in the retina and has been previously investigated as a potential marker for the condition. A second study presenting their results at AAIC 2016 compared different methods for visualising amyloid protein deposits in dissected eyes as well as in dogs that had symptoms of Alzheimer’s disease. One of the imaging techniques tested – polarization imaging – was shown to be a non-invasive and sensitive way to identify amyloid deposits in the retina.

Dr Clare Walton, Research Manager at Alzheimer’s Society, said:

'Changes in the brain associated with dementia can begin several years before any memory symptoms appear. This research suggests that some of these changes happen in the retina of the eye too, which could give us a relatively easy, non-invasive way to spot them early.

'Eye tests are fairly common for older people, so there is great potential to incorporate additional tests into their regular check-up. These tests could help to identify people at risk of dementia who would benefit from further investigation but will not become a primary way to diagnosis the condition.

'Large studies like the UK Biobank are vital to allow researchers to uncover subtle biological changes, such as these described in the eye, that can be used as early indicators of dementia. These studies are always looking for more people – both with memory problems and without – to participate and we encourage people to sign up to take part in dementia research via the Join Dementia Research website.'