Image caption The impact of macular degeneration on vision

People who regularly take aspirin for many years, such as those with heart problems, are more likely to develop a form of blindness, researchers say.

A study on 2,389 people, in the journal JAMA Internal Medicine, showed aspirin takers had twice the risk of "wet" age-related macular degeneration.

The disease damages the 'sweet spot' in the retina, obscuring details in the centre of a patient's field of vision.

The researchers said there was not yet enough evidence to change aspirin use.

Taking low doses of aspirin every day does reduce the risk of a stroke or heart attack in patients with cardiovascular disease. There are even suggestions it could prevent cancer.

One in 10 people in the study, conducted at the University of Sydney, were taking aspirin at least once a week. On average the participants were in their mid-60s.

Eye tests were performed after five, 10 and 15 years.

The evidence is now accumulating about the association of aspirin and wet AMD, however, it is not overwhelming at this point Macular Society

By the end of the study, the researchers showed that 9.3% of patients taking aspirin developed wet age-related macular degeneration (AMD) compared with 3.7% of patients who did not take aspirin.

Their report said: "The increased risk of [wet] AMD was detected only after 10 or 15 years, suggesting that cumulative dosing is important.

"Given the widespread use of aspirin, any increased risk of disabling conditions will be significant and affect many people."

Wet AMD is caused by blood vessels growing in the wrong place. They cause swelling and bleeding which damages the retina.

The process can happen very quickly with vision being damaged in days. Age, smoking and a family history are the main risk factors.

High-risk

There are already known risks of aspirin such as causing internal bleeding. The research team suggest the risk of damaging eyesight "may also need to be considered".

They acknowledge that for most patients there is "insufficient evidence" to change how aspirin is prescribed.

However, they suggested using the drug may need to be reappraised in high-risk patients such as those with wet AMD in one eye already.

Prof Jie Jin Wang, an expert in vision research at Sydney University in Australia, said this was something doctors might want to discuss with high-risk patients.

The Macular Society said: "The evidence is now accumulating about the association of aspirin and wet AMD, however, it is not overwhelming at this point.

"For patients at risk of cardio-vascular disease, the health risks of stopping or not prescribing aspirin are much higher than those of developing wet AMD.

"Patients who are taking aspirin because their doctor has prescribed it should not stop taking it without consulting their doctor first."

Matthew Athey, from the RNIB charity, said any concerns should be discussed with a family doctor.

"However, this is interesting research as age-related macular degeneration (AMD) is the leading cause of sight loss in the UK, and this study could contribute to our understanding about why some people may develop 'wet' type macular degeneration.

"Further research is needed to clarify and investigate some of the issues raised in the study, however this association may be valuable for doctors in the future when considering aspirin for their patients."