Cataract surgery might not speed up age-related macular degeneration as previously thought, a new study suggests.

Cataracts occur when the lens of the eye becomes cloudy and are a leading cause of blindness worldwide. Age-related macular degeneration, or AMD, is the leading cause of blindness among Americans age 65 and older, researchers said in the November issue of the Archives of Ophthalmology.

'Our findings do not support the hypothesis that cataract surgery accelerates the progression of AMD.'— Study authors

AMD attacks the macula, a small area in the centre of the retina, preventing sufferers from seeing fine details.

Ophthalmologists have long debated whether cataract surgery increases the risk of progression to an advanced form of AMD that involves the formation of new blood vessels, known as neovascular or wet AMD.

There is no cure for neovascular AMD, but there are treatments.

In the study, Li Ming Dong of Stony Brook University School of Medicine in New York, and colleagues looked at 71 individual eyes of patients without neovascular AMD, before cataract surgery and one week and one year after the surgery.

The team excluded five eyes that showed signs of neovascular AMD at the week follow-up that may have been present earlier but couldn't be detected before the cataract surgery. Another eye was excluded because of missing documentation needed for the study.

Of the remaining eyes, three, or 4.6 per cent, progressed to neovascular AMD between one week and a year after the surgery, compared with one eye, or three per cent, among cataract-free eyes over the same time period.

"Our findings suggest that previous reports of the association or progression of non-neovascular AMD to advanced AMD after cataract surgery could be biased," the researchers wrote.

Research inconsistencies

Subtle signs of neovascular AMD or geographic atrophy, also known as dry AMD, may be obscured before cataract surgery.

In such cases, the AMD may contribute to vision loss but may "erroneously be ascribed to the cataract and contribute to a decision to proceed with cataract surgery," the team said.

"Our findings do not support the hypothesis that cataract surgery accelerates the progression of AMD," they concluded.

Since the late 1980s, there have been several reports of an association between cataract surgery and AMD, Dr. Barbara Klein of the University of Wisconsin–Madison said in an accompanying editorial.

Differences in study design might account for the conflicting reports, Klein said.

"A straightforward discussion of the inconsistencies of the research findings to date … would help both the patient and his or her physician to make a more informed decision," she concluded.

"Until we have better information regarding the risk of developing AMD in those undergoing cataract surgery, it is the best we can do for our patients."