Diabetes medication prescribed to millions can help protect against disease which has left 600,000 struggling with blindness, study finds

A cheap diabetes drug taken by millions could ward off the most common cause of blindness, a study has found. 

Doctors have found that the type 2 diabetes medication metformin, which costs the NHS just 35p per pill, is associated with a lower progression of age-related macular degeneration (AMD).

AMD rarely causes permanent blindness, but it does cause blurry and distorted vision and blind spots, which can make reading and recognising faces difficult.

It is the leading cause of sight loss in older people, and it’s estimated that 600,000 people in the UK struggle with the condition; the NHS claims that at 60, around one in every 2,000 people has AMD, but by the age of 90 it affects one person in five. 

There is no specific cause, but age and lifestyle factors including smoking, obesity, drinking alcohol and eating a diet high in processed foods and low in nutrient-dense fruits and vegetables increase the chances of it developing.

It usually first affects people in their 50s and eventually causes the light-sensitive tissue to die off or be damaged by abnormal blood vessel growth – currently, there is no treatment licensed for AMD – but researchers claim that metformin could be an accessible treatment option.

The new study, from the University of Liverpool and published in the BMJ, found that diabetic people aged 55 and over who were taking metformin were 37 per cent less likely to develop intermediate AMD over five years compared to those not taking metformin. 

They looked at images taken of the eyes of 2,545 people who had attended the routine diabetic eye disease screening programme in Liverpool over a five year period.

Each patient had retinal photographs taken in 2011 and again in 2016, which were graded by eye specialists using a recognised system and classified as Early AMD, Intermediate AMD and Late AMD which is the stage most likely to cause serious vision loss. 

Using GP records to establish which of the cohort were prescribed metformin, the researchers then compared how often AMD developed or got worse in people on the drug versus those not on it.

They concluded that in people with diabetes, taking metformin was linked to a significantly lower risk of developing intermediate AMD over 5 years. 

However, it did not reduce the chance of developing early AMD, or slow progression from early AMD to more advanced stages. 

Other limitations noted by the study authors were that the metformin group was slightly younger and healthier in some ways, and there was limited information about the exact metformin dose and how long people had been taking it. 

Furthermore, there was no information about the cohort’s diet or if they regularly took any vitamin supplements, and the study results only apply to people with diabetes, not the general population.  

They theorised that metformin might help protect the retina through its anti-ageing and anti-inflammatory effects and further investigations are warranted.

Dr Nick Beare, an eye doctor who led this research, said: ‘Most people who suffer from AMD have no treatment, so this is a great breakthrough in our search for new treatments. 

‘What we need to do now is test metformin as a treatment for AMD in a clinical trial. Metformin has the potential to save many people’s sight.’

Metformin, which has been in use for over 60 years, lowers the amount of sugar the liver pumps out and helps the body respond to insulin, a hormone which regulates blood sugar levels.

It has proved to be a highly versatile medication, showing significant promise in managing a variety of other conditions

Other recent studies have found that metformin helped prevent acute myeloid leukaemia, a blood cancer that quickly kills about four out of five patients.

Scientists first uncovered the link between the drug and anti-cancer benefits in experiments on mice, but then found the same result in humans.

Intermediate and advanced AMD affects 10-15 per cent of people over 65, which equates to 1.1 to 1.8 million people in the UK. 

 It is the most common cause of blindness in high-income countries and the annual cost of AMD is estimated to be £11.1 billion in the UK. 

Advanced AMD involves significant central vision loss and is classified into two types: dry and wet.

Dry AMD involves the gradual degeneration of macular cells, leading to slowly enlarging blind spots. 

Wet AMD is characterised by rapid, aggressive and severe central vision loss caused by abnormal, leaky blood vessels developing under the retina.

Research into possible new treatments for AMD is ongoing, with recent studies showing that a tiny chip implanted in the back of the eye can effectively restore vision loss.