Drugs which slow the progress of Alzheimer's disease may protect patients at risk of eye damage from glaucoma, say researchers.
Pressure builds up in the eye
The University College London team said experiments suggested there were strong similarities between the conditions.
But they stress that the 500,000 UK people with glaucoma are not at higher risk of Alzheimer's.
The research, published in Proceedings of the National Academy of Sciences, is welcomed by a leading eye charity.
At the moment, little is known about the origins of glaucoma, although patients are offered operations and drug treatment to treat raised pressure within the eye, which can harm eyesight by interfering with blood supply to the optic nerve.
Some glaucoma patients have normal eye pressure, but still lose their eyesight, and the research team, led by Dr Francesca Cordeiro, said that the link with Alzheimer's could offer more clues to glaucoma's causes, and lead to treatments.
They were able to look closely at nerve cell damage in the retina of the eye, and come up with evidence that the protein beta-amyloid - which causes the so-called damaging "plaques" in the brains of Alzheimer's patients - is also responsible for harm to the optic nerve.
Dr Cordeiro said: "We've seen for the first time that there is a clear link between what causes Alzheimer's disease and one of the basic mechanisms behind glaucoma."
Pharmaceutical companies are already trying to produce drugs to help Alzheimer's patients by slowing or reversing the build-up of beta-amyloid plaques on their brains.
The UCL researchers tried a combination of these drugs on rats, and found that they reduced the rate of nerve cell death in the eye.
Dr Cordeiro said: "We are trying a new approach which has never been tried before - our success in treating glaucoma in the lab by combining different Alzheimer's treatments represents a brand new treatment strategy."
However, she said that people with glaucoma should not worry that they were destined to suffer from Alzheimer's.
"This doesn't mean that everyone with Alzheimer's will develop glaucoma or vice versa - glaucoma has a number of risk factors."
David Wright, the chief executive of the International Glaucoma Association, said that the research findings were "interesting".
"We have been searching for an efficient 'neuroprotective' agent for glaucoma patients.
"If we have a drug that is neuroprotective within the brain for Alzheimer's patients, there's a good chance it will work in the eye, as the eye is simply an outgrowth of brain material."