People taking statins to protect against a heart attack or stroke are far more likely to be diagnosed with cataracts, claim scientists.
The condition causes cloudy patches on the lens at the front of one or both eyes, making vision blurred or misty.
It is a leading cause of blindness and at least 200,000 people in the UK are treated each year.
A team from the San Antonio Military Medical Center in Texas compared the eyesight of thousands of patients who took statins and those who didn’t.
In the study, published in the journal JAMA Ophthalmology, they concluded: “The risk for cataract is increased among statin users as compared with non-users.
“The risk-benefit ratio of statin use, specifically for primary prevention, should be carefully weighed and further studies are warranted.”
Clara Eaglen, for leading charity RNIB, said: “This is interesting research as cataracts are very common in older people with one in three over-65s being diagnosed in the UK.
“Many people are prescribed statins to help lower cholesterol and if they have any concerns they should discuss this with their GP before taking any action.
“Cataracts can prevent some people from driving, undertaking work that requires fine detail and recognising faces.
“Any research which could help prevent unnecessary sight loss through eye conditions such as cataracts is a welcome step forward.”
Over time, the cloudy patches caused by cataracts grow bigger, causing vision to rapidly deteriorate.
The condition is linked to smoking, poor diet and some health conditions including diabetes.
If left untreated, it can lead to blindness, although this is now rare in Britain.
People with mild cataracts improve their vision using glasses but eventually they may need surgery.
Cataract surgery is safe and cost-effective and is the third most common procedure carried out by the NHS.
Previous research looking at the link between statins and cataracts has provided conflicting results.
A study by experts at Tel Aviv University in Israel in 2010 claimed that statins can actually cut the chances of developing cataracts by almost 40 per cent. They found that men aged between 45 and 54 who took the cholesterol-lowering pills virtually every day reduced their risk of cataracts later in life by 38 per cent compared with those who took them rarely.
In women of the same age the risk was reduced by about 18 per cent.
Statins, taken by about eight million people in the UK, have been hailed as a wonder drug for lowering cholesterol levels and preventing tens of thousands of heart attacks and stroke each year.
Heart experts say that if five million more people took them it would cut heart attacks and stroke by 10,000 a year, saving 2,000 lives.
Others warn that not enough is known about the side-effects, which evidence suggests can range from muscle aches and tummy upsets to liver and kidney damage.
Yet most cardiologists agree that when used according to current guidelines, the benefits of taking the pills far outweigh the risks.