Blindness: What triggers vision loss in age-related macular degeneration (AMD)?
This research was completed on 30 April 2011
Published on 31 January 2008
Age-related macular degeneration (AMD) is the leading cause of blindness in industrialised countries, but our understanding of why so many people develop this distressing condition as they get older is far from complete.1 Professor Alan Stitt, of Queen’s University Belfast, has identified some of the molecular processes that may trigger damage to the eye and vision loss in AMD. His findings might help in the search for new diagnostic tests and treatments in the battle to save people’s sight.
What is the problem and who does it affect?
Over half of the people who are certified as blind or partially sighted in the UK have lost their vision to AMD.2 Most are over 50 years old and their numbers are set to rise dramatically as the population ages.3
“AMD can have a devastating effect on people’s lives,” explains Professor Stitt. “Typically, the first thing people notice is some blurring or distortion of their central vision. If the disease becomes advanced, they develop a blank patch or dark spot right in the centre of their field of view.”
People with advanced disease can’t read, write, watch television, drive or see the faces of loved ones properly. Many worry about losing their independence.
There are two types of AMD – ‘wet’ and ‘dry’. The wet form, which affects 10-15 per cent of sufferers, typically progresses the fastest.4
“There is no effective treatment for dry AMD”, explains Professor Stitt. “There are exciting new treatments that can benefit people with wet AMD, and these have been proven to prevent the progression to blindness. However, this treatment does not always work well for everyone, it cannot restore vision if the eye is already permanently scarred, and it can cause side effects. We urgently need new ways to diagnose AMD earlier and better ways to treat it.”
What did the project achieve?
Vision loss in AMD results from progressive damage to the back of the eye, which typically goes unnoticed until people start to lose their sight.
“Although we know what sort of damage people with AMD have in their eyes, we do not fully understand the disease processes that cause it,” explains Professor Stitt. “While we recognise genetic and environmental causes, we do not fully understand why some people develop AMD as they get older while others do not.”
Professor Stitt has been investigating which molecules and cells play a role in the development of wet AMD. He has discovered that two molecules – called S100B and RAGE – and certain immune cells seem to be particularly important and has started to piece together what these molecules and cells do.
“Our work provides compelling evidence that drugs that target RAGE might be able to prevent vision loss in AMD,” explains Professor Stitt. “Several such drugs have already been developed and some are being evaluated in clinical trials in other age-related conditions, including Alzheimer’s disease and complications of diabetes.”
Professor Stitt plans further laboratory studies into the role of RAGE, essential groundwork that might eventually lead to new diagnostic tests and treatments for AMD in the battle to save people’s sight.
What are the researchers’ credentials?
Professor Alan Stitt is Scientific Director of a large, internationally recognised centre of excellence in experimental ophthalmology. His team’s integrated programme of research tackles the major causes of blindness in the UK. On a personal level, Professor Stitt’s mother has severe vision loss from AMD, which gives him extra motivation to develop new treatments.
|Project Leader||Professor Alan W Stitt PhD|
|Location||Centre for Vision Science, Royal Victoria Hospital, Queen's University Belfast|
|Grant awarded||31 October 2007|
|Start date||1 January 2008|
|End date||30 April 2011|
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1. World Health Organization. Prevention of blindness and visual impairment. Priority eye diseases. Age related macular degeneration. http://www.who.int/blindness/causes/priority/en/index8.html. Website accessed 27 June 2012.
2. Owen CJ et al. The estimated prevalence and incidence of late stage
age related macular degeneration in the UK. British Journal of Ophthalmology 2012; 96 (5): 752-6.
3. British Journal of Ophthalmology. Press Release. UK cases of progressive sight loss condition (AMD) set to rise a third by 2020. http://bjo.bmj.com/content/suppl/2012/02/14/bjophthalmol-2011-301109.DC2.... Website accessed 27 June 2012.
4. RNIB. Age-related macular degeneration (AMD). http://www.rnib.org.uk/eyehealth/eyeconditions/conditionsac/pages/amd.aspx Website accessed 26 June 2012