Serious, potentially blinding complications from cataract eye surgery are uncommon, and have been declining since the 1990s, a new U.S. study finds.

A cataract is a clouding of the eye’s lens, usually caused when proteins in the lens start to clump up as a person ages. Cataract removal is the most common type of surgery in the U.S., with more than 3 million procedures done each year.

While the surgery is generally considered safe, there can be sight-threatening complications - including severe inflammation in the eye, bleeding, and detachment of the retina, the light-sensing tissue in the back of the eye.

But those problems are uncommon and appear to be on the wane, according to new findings reported in the journal Ophthalmology.

Researchers found that for every 1000 Medicare patients who had cataract surgery in 2005 or 2006, four had at least one serious complication in the following year. That compared with six of every 1000 a decade earlier, in 1994 and 1995.

When the researchers took risk factors for complications into account - including having other chronic health conditions - people who had surgery in the mid-1990s were 21 percent more likely to have a serious complication than those who had surgery in recent years.

“Our analysis confirmed that cataract surgery is a safe surgical procedure with low risks of severe adverse events, and that the safety profile of this procedure has continued to improve over the past decade,” said lead researcher Dr. Joshua D. Stein, of the University of Michigan in Ann Arbor, in an email to Reuters Health.

It’s hard to tell why the improvement is happening, based on information from Medicare claims alone, Stein said.

But he and his colleagues suspect the credit should largely go to technical advances in how cataract surgery is done.

These days, cataract removal is usually done via a technique called “phacoemulsification.” The surgeon makes a small incision in the eye’s outer membrane, then inserts a tiny probe. The probe emits sound waves that break up the lens, which is then suctioned out and replaced with an artificial lens.

The same type of procedure was also done in the 1990s. But improved equipment and instruments may largely explain the decline in severe complications, according to Stein.

There are, though, certain patients at relatively higher risk of complications from cataract surgery, the study found.

They included patients with proliferative diabetic retinopathy - an advanced stage of diabetes-related damage to the tiny blood vessels of the retina. While their risk of severe complications was still low, it was 62 percent higher than in patients without proliferative diabetic retinopathy.

That, Stein’s team writes, suggests that when people with diabetic retinopathy have cataracts, it might be better to consider surgery sooner rather than later - before the retinopathy gets worse.

Patients having certain other eye procedures at the same time as cataract surgery were also at increased risk of complications.

But Stein said it’s tough to interpret that finding.

The researchers had no information on whether patients’ additional procedures were pre-planned, or whether they were done to manage a complication during cataract surgery. So it’s not clear that combination surgeries were a risk factor for complications.

“Before surgeons and patients jump to any conclusions about this specific finding,” Stein said, “I think that additional studies are warranted, using other data sources which can help decipher some of the underlying reasons for this trend we are observing.”

The researchers say future studies should also look into ways to further curb surgery complications in patients who remain at relatively greater risk, like those with advanced diabetic retinopathy.

In the U.S., it’s estimated that half of people who live to the age of 80 will either have cataracts or have cataract surgery, at a cost of $1,500 to $3,000 per surgery.

SOURCE: Ophthalmology, online June 2, 2011.