A research published ahead of print in the British Journal of Ophthalmology suggests certain types of drugs prescribed to lower blood pressure seem to increase the risk of corrective cataract surgery.

Cataracts cause blurred vision, and if left untreated can lead to blindness. They cloud over the lens at the front of the eye. In order to produce a sharp image, the lens must be transparent for light to pass through to the retina at the back of the eye. Around a third of the UK population over the age of 65 has a cataract in one or both eyes. Approximately 300,000 corrective procedures are carried out each year.

During five to ten years Australian researchers tracked the eye health of over 3,500 people. When the study began between 1992 and 1994, all participants were at least 49 years old.

There was confirmation of a borderline association between the use of beta blockers and calcium channel blockers, and the risk of cataract. Both of them are classes of blood pressure lowering drug.

For two other types of drug used to lower blood pressure, diuretics (water pills) and ACE inhibitors, no such connection was found.

The researchers studied influential factors, such as age, smoking, and use of steroids, which are known to increase cataract risk. They found that ACE inhibitors and beta blockers considerably predicted the likelihood of cataract surgery.

The likelihood for individuals taking beta blockers to undergo cataract surgery was 61 percent. And for those taking ACE inhibitors to lower their blood pressure, the likelihood was 54 percent.

Patients taking beta blockers for conditions other than high blood pressure were more than twice as likely to have the procedure.

The authors remark there has been argument that high blood pressure itself could be responsible for the development of cataracts, but the evidence to verify this has been inconsistent.

According to experimental research, beta blockade could have an effect on the lens transparency by modifying the proteins and altering the delicate cellular balance of the lens.