Eye Health

19 August 2011

Severe vision loss

More than half of patients who have a trabeculectomy for glaucoma may suffer from temporary, sometimes severe vision loss afterward, suggests a new study.


More than half of patients who have a trabeculectomy for glaucoma may suffer from temporary, sometimes severe vision loss afterward, suggests a new study. A smaller proportion, about 8%, could have some degree of permanent vision loss, researchers found.

Dr Brian Francis of the Keck School of Medicine at the University of Southern California, one of the study's authors, said that trabeculectomy is typically reserved for patients with severe, refractory glaucoma.

He estimated that only about 5% to 10% of glaucoma patients will need the surgery – but they will sometimes need it multiple times.

The procedure, also called glaucoma filtration surgery, involves creation of a small hole toward the front of the eye to drain out extra fluid, which is eventually absorbed by the bloodstream.

"We found a pretty high number of (people with) mild to moderate vision loss after trabeculectomy, but the majority of them recovered over time," Dr Francis said.

"The surprising thing was that we found the time to recovery could be quite lengthy," he added.

Trabeculectomy statistics in previous years

He and his colleagues looked back at the medical records of 262 patients who had a trabeculectomy between 1999 and 2003 on a total of 301 eyes. They followed the patients, and their reports of post-surgery vision, for up to two years.

Transient postoperative vision loss occurred in 170 eyes (57%). Whether mild or severe, vision loss typically took an average of two to three months to improve, the researchers reported this month in Archives of Ophthalmology.

In some cases, temporary vision problems took up to two years to resolve. But in 24 eyes (8%), vision loss was permanent. It was mild or moderate in 13 patients and severe in the other 11.

Dr Francis suggested the surgery could be adding stress to an already ailing eye. In people with mild or moderate glaucoma, he said, there's less of a risk of vision loss from any pressure-reducing procedure.

With glaucoma, "the earlier you catch the disease and start treating it, the better your prognosis is going to be", he said.

For those with severe glaucoma who may need the surgery, however, the findings provide "reassurance that this is a small percentage" with permanent vision loss, Dr Francis said. "But it is a risk factor that has to be discussed with the surgeon."

And for some patients who have had the surgery in the last year or so and are suffering from decreased vision, they can be hopeful that those problems could still improve, he added.

(Reuters Health, Genevra Pittman, August 2011) 

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Megan Goodman qualified as an optometrist from the University of Johannesburg and is currently practising at Tygerberg Academic Hospital in Cape Town. She has recently completed a Masters degree in Clinical Epidemiology at Stellenbosch University. She has a keen interest in ocular pathology and evidence based medicine as well as contact lenses.

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