A blood test is set to save the sight of older people by detecting a common eye disease before symptoms even start.
For the five million people across the world with age-related macular degeneration (AMD), the first sign is often early sight loss.
By the time they notice dark spots in their vision or words which disappear from the page when reading, a lot of the damage has already been done.
However ophthalmologists say there is now a blood test for the disease – the leading cause of blindness in British people aged 50 and over.
This could save people’s sight by picking it up before symptoms strike, allowing them to get vital injections earlier. These injections slow down deteriorating eyesight in people with the ‘wet’ form of AMD by blocking the overgrowth of leaky blood vessels in the eye.
For the more than 600,000 people in Britain with age-related macular degeneration, the first sign is often a loss of vision
DRUGS TO PREVENT GOING BLIND?
Millions of people could be prevented from going blind by drugs designed to treat depression and strengthen bones, research suggested last year.
In tests on mice, drugs already on sale for other conditions prevented the first stage of AMD.
The US researchers showed two mechanisms that would normally keep the RPE healthy, cells at the back of the eye, are weak in AMD.
They then identified drugs that boosted the protection.
These included an anti-depressant called desipramine and drugs used to treat osteoporosis a – condition in which bones become fragile.
Previous research has found that long-term users of the drugs are less likely to develop AMD.
‘Allow us to intervene sooner and ultimately provide better care’
The blood test, developed by a team led by Massachusetts Eye and Ear Infirmary, is based on 87 fatty proteins which were linked to the eye disease in 90 patients.
Co-author Dr Joan Miller, chief of ophthalmology at Massachusetts General Hospital, and a professor at Harvard Medical School, said: ‘Because the signs and symptoms of early stage AMD are very subtle, with visual symptoms only becoming apparent at more advanced stages of the disease, identification of biomarkers in human blood plasma may allow us to better understand the early to intermediate stages of AMD so we may intervene sooner, and ultimately provide better care.’
It is estimated one in 10 pensioners in the UK have some degree of age-related macular degeneration. By 2020, it is predicted almost 700,000 people, mainly women, will be in the late stages of the disease. One million suffer in the US.
Their best hope of discovering it currently is for an optician to pick it up through a routine eye test.
A blood test however offers hope of older people being screened for the disease. Those most at risk, who include smokers and those with a family history of AMD, could be alerted to the changes in their eyes sooner.
Blood tests could even be rolled out to people believed but not proven to be in greater danger of getting it. They include people exposed to a lot of sunlight over a lifetime, those with a history of high blood pressure and people who drink a lot or are obese.
‘We believe this work will launch the era of personalised medicine in AMD‘
The US researchers took blood samples from 90 people with early, intermediate and late-stage AMD and 30 who were free of the disease to check for common markers in their blood.
They found 87 tiny molecules, most of which were fatty proteins called lipids, present at significantly different levels in the blood of people with AMD.
It is believed lipids, of which cholesterol is one type, may help to cause AMD, building up yellow deposits in the retina. One type of lipid linked to AMD has also been connected to Alzheimer’s, which is a neurodegenerative disease too.
The results have the potential to improve earlier diagnoses for AMD patients, and may lead to more treatment options.
Co-author Dr Deeba Husain, a retina specialist at Masachusetts Eye and Ear Infirmary, said: ‘We believe this work will help launch the era of personalised medicine in treatment of AMD.
‘Our work gives us a novel biomarker for early diagnosis, and it gives us clues to differentiate the progressers from non-progressers. This research also gives us insight into important role of lipids in AMD, which will provide novel targets for treatment in the early stage of disease, thus preserving vision in AMD.’
Cathy Yelf, chief executive of the Macular Society, the UK charity for people affected by AMD, said: ‘This is a very interesting study in a relatively new area of AMD research. AMD develops very slowly and by the time people have noticeable sight loss it is proving very difficult to treat.
‘It is a priority in AMD research to find the earliest signs of the condition so that we can look for a therapy that will stop it developing into advanced, blinding disease.’