Eye drops containing cholesterol-busting drugs could combat one of the most common causes of blindness, according to new research.
Age-related macular degeneration (AMD) is a painless condition which leads to the gradual loss of the central vision.
It is thought that aging, smoking and genetics can all increase a person’s chance of developing the condition.
However, it is also thought to be triggered by harmful blood fats.
Experiments on mice have found that deposits of this cholesterol contribute to the development of the condition.
Patients who have hardened arteries – which are also caused by harmful blood fats – often are prescribed medications to lower cholesterol and keep arteries clear.
Now, a study published in the journal Cell Metabolism suggests that some of those same drugs could be used to treat patients with macular degeneration.
Professor Rajendra Apte said: ‘Based on our findings, we need to investigate whether vision loss caused by macular degeneration could be prevented with cholesterol-lowering eye drops or other medications that might prevent the build-up of fats beneath the retina.’
An estimated 500,000 people in the UK suffer from AMD, and 40 per cent are over the age of 75.
The new research centres on immune cells known as macrophages that remove cholesterol and fats from tissues.
In macular degeneration, the excessive build-up of cholesterol begins to occur as we age, and our macrophages begin to malfunction.
In the less aggressive form of AMD, doctors examining the eye can see lipid deposits beneath the retina.
As those deposits become larger and more numerous, they slowly begin to destroy the central part of the eye, interfering with the vision needed to read a book or drive a car.
Professor Apte’s researchers at the University of Washington found macrophages taken from old mice and patients with macular degeneration have inadequate levels of a protein called ABCA1 which transports cholesterol out of cells.
As a result, the old macrophages accumulated high levels of cholesterol and could not inhibit the growth of the damaging blood vessels that characterise the more advanced form of the disorder.
But when the macrophages were treated with a substance that helped restore levels of ABCA1, the cells could remove cholesterol more effectively, and the development of new blood vessels was slowed.
Co-author, Dr Abdoulaye Sene, said: ‘We were able to deliver the drug, called an LXR agonist, in eye drops. And we found we could reverse the macular degeneration in the eye of an old mouse.
‘That is exciting because if we could use eye drops to deliver drugs that fight macular degeneration, we could focus therapy only on the eyes, and we likely could limit the side effects of drugs taken orally.’
Since macrophages are important in thickening of the arteries and in the formation of new blood vessels around certain types of cancerous tumours, the same pathway also might provide a target for more effective therapies for those diseases.
Professor Apte said: ‘We have shown we can reverse the disease cascade in mice by improving macrophage function, either with eye drops or with systemic treatments.
‘Some of the therapies already being used to treat thickening arteries target this same pathway, so we may be able to modify drugs that already are available and use them to deliver treatment to the eye.’