By Adrian Galbreth
Age-related macular degeneration (AMD) is one of the leading causes of blindness in the western world and has been the subject of many studies over the years, though new research carried out in Ireland looks closer than most to preventing the development of the condition.
According to experts at Trinity College Dublin, they have discovered that a part of the immune system called the inflammasome is involved in regulating the development of AMD.
In a new study published this week in the international medical journal Nature Medicine, the specialists claim that controlling the inflammatory component IL-18 in cases of AMD could prevent the development of the disease.
The breakthrough study has already received the backing of Science Foundation Ireland, the American Health Assistance Foundation (AHAF), the Health Research Board (HRB) and Fighting Blindness Ireland.
A recent study carried out by Access Economics found that AMD is the most prevalent of the five leading causes of sight loss in the UK, which also include refractive error, cataracts, glaucoma and diabetic retinopathy.
Overall, 16.7 per cent of people with sight loss have age-related macular degeneration, with advanced suffers unable to enjoy everyday things such as reading, watching TV, going to the cinema, driving or using a computer.
In the Dublin study, researchers explained that the key diagnostic feature of AMD is the presence of "drusen", the yellowish/white deposits in the central region of the retina called the macula that are often identified in eye exams.
Normally, dry AMD is characterised by the presence of excessive amounts of drusen and there are currently no forms of treatment other than recommended lifestyle changes, such as giving up smoking.
The scientists note that a substantial number of cases of the "dry" form of AMD can progress to the "wet" form, where blood vessels underneath the retina begin to grow, leading to central blindness.
Trinity College scientists Dr Sarah Doyle and Dr Matthew Campbell, co-authors of the report, say living with the advanced form of this condition is akin to holding two coins immediately in front of the eyes, which results in seeing a single large black circle blocking out central vision.
However, in the new study, the experts observe that drusen accumulating in the macula can lead to the production of two inflammatory components termed IL-1beta and IL-18.
The results were based on studies involving drusen isolated from donor AMD eyes in tandem with pre-clinical studies on models of the disease, Dr Campbell explained.
He added: "Traditionally, inflammation in the retina or indeed the eye in general is not beneficial and is a pathological hallmark of many eye diseases, including AMD.
"However we have identified, that one inflammatory component termed IL-18 acts as a so-called anti-angiogenic factor, preventing the progression of wet AMD."
Dr Doyle said that the progression from "dry" to "wet" AMD appears to be mediated by the inflammatory component IL-18, with the results directly suggesting that controlling or augmenting the levels of IL-18 in the retinas of patients with dry AMD could prevent the development of the wet form of disease.
"This leads us to an exciting new prospect for a novel therapy for AMD" the expert added.
The study was carried out across multiple sites, including Trinity College's Ocular Genetics Unit under director Professor Pete Humphries and at the laboratories of Professor Luke O'Neill at the Trinity Biomedical Sciences Institute, along with Cole Eye Institute at Cleveland, Ohio, under Professor Joe Holyfield.
The experts claim that the findings could have major impacts on the way in which AMD is both discovered and stopped, and could prevent people predisposed to the condition from developing it entirely.
by Adrian Galbreth