SIMPLE eye and smell tests could be used to spot dementia years before sufferers experience memory symptoms, new research suggests.

Researchers at Moorfields Eye Hospital and the UCL Institute of Ophthalmology found a link between poor cognitive ability – a “clear warning sign” of the early stages of Alzheimer’s – and the thickness of people’s retinal nerves.

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In a trial of more than 33,000 participants who had tests on memory, reaction time and reasoning, eye scans showed the nerve fibre layer was “significantly thinner” among those who performed poorly on cognitive tests.

The findings, presented at the Alzheimer’s Association International Conference in Canada, are key to diagnosing the condition early in order to find treatments.

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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 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.”

While the tests could help with early intervention, it is not expected to be a primary way to diagnose the condition, she added.

Dr Simon Ridley, director of research at Alzheimer’s Research UK, said the tests could help identify people at risk of memory decline, but more research was needed.

He said: “While this study did not look at changes in people with dementia, it does show that thinning of a layer of cells in the retina is associated with reduced cognitive performance.

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"Further work is required to see whether thinning of the retinal nerve fibre layer is predictive of cognitive decline and dementia, to assess better whether nerve cell loss in the eye could be a potential early marker of the condition.”