A pioneering new test to detect glaucoma ten years before symptoms start to show may also be able to diagnose dementia.
Researchers at the University College London and Western Eye Hospital found by examining nerve cell death in eyes, they may also be able to predict several neurodegenerative conditions.
Death of cells in the retina at the back of the eye, called apoptosis, can cause loss of sight in patients with glaucoma.
The common eye condition happens when the optic nerve, which connects the eye to the brain, becomes damaged.
According to the Glaucoma Research Foundation, it’s now viewed as a disease of the brain - a neurodegenerative disease - rather than simply an eye condition.
In neurodegenerative conditions - which also includes dementia - increasing numbers of nerve cells are lost as the disease progresses.
The eye test could indicate multiple degenerative neurological conditions, including Parkinson's and multiple sclerosis, leading to an earlier diagnosis.
Because the glaucoma test could be done as part of a routine visit to the optometrists, many people may benefit from this research.
If glaucoma is left untreated it can lead to a loss of vision and potentially blindness.
It occurs when the fluid in the eye cannot drain properly, increasing pressure inside the eye and on the optic nerve.
While it can be picked up during an eye test, many sufferers don’t realise they have it because symptoms develop very slowly over several years - the first sign is often a loss of peripheral vision.
Currently treatment can only help to stop vision from getting any worse - not reverse it - but these findings could mean the condition is diagnosed without any symptoms at all.
Professor Francesca Cordeiro at UCL Institute of Ophthalmology said: "Detecting glaucoma early is vital as symptoms are not always obvious. Although detection has been improving, most patients have lost a third of vision by the time they are diagnosed.''
"Now, for the first time, we have been able to show individual cell death and detect the earliest signs of glaucoma. While we cannot cure the disease, our test means treatment can start before symptoms begin.
"In the future, the test could also be used to diagnose other neurodegenerative diseases."
In fact, detection of glaucoma could happen a decade before onset symptoms.
Professor Philip Bloom, Chief Investigator at Western Eye Hospital, part of Imperial College Healthcare NHS Trust, added: "Treatment is much more successful when it is begun in early stages of the disease, when sight loss is minimal.''
"Our developments mean we could diagnose patients 10 years earlier than was previously possible."
Initial clinical trials have been carried out on a small number of glaucoma patients, and researchers will next investigate to what extent a similar test could predict other neurodegenerative conditions.''