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Cataract surgery raises risk of failure of prior trabeculectomy

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – Trabeculectomy to relieve intraocular pressure (IOP) is more likely to fail if patients subsequently undergo cataract surgery, particularly if the interval between operations is relatively short, a multicenter team reports in Ophthalmology online October 10.

“Delaying cataract surgery in eyes that have had a previous trabeculectomy increases the chances of successful IOP control,” the authors conclude.

Dr. Tin Aung, with the Singapore National Eye Center, and colleagues point out that glaucoma and cataracts often coexist, and the options are to treat one condition before the other or both simultaneously. “Analyzing the effect of cataract surgery on eyes that have undergone a previous trabeculectomy will help in deciding the best course of action in patients with glaucoma and cataract,” they explain.

To that end, the team conducted a study involving 235 glaucoma patients who had a single trabeculectomy. Cataract surgery with intraocular lens implantation was subsequently performed in 124 of these patients who had significant lens opacity. The interval between procedures ranged from 4.6 to 81.9 months, median 21.7 months.

During follow-up, 22 patients in the cataract surgery group experienced trabeculectomy failure, defined as an IOP of greater than 21 mm Hg on the second of two consecutive visits after the first 6 weeks.

“Adjusting the analysis for the presence of glaucoma, diabetes, trabeculectomy augmentation, pretrabeculectomy IOP, number of antiglaucoma drops instilled pretrabeculectomy, number of posttrabeculectomy steroid drops, and age made no substantial difference to the estimated influence of time from trabeculectomy to cataract surgery (hazard ratio, 1.73; p=0.03), which shows that cataract surgery after trabeculectomy increased the risk of trabeculectomy failure,” Dr. Aung and colleagues report.

They were also able to calculate hazard ratios for risk of trabeculectomy failure at various time points at which cataract surgery was performed after trabeculectomy, compared to patients who did not have cataract surgery. Those hazard ratios were 3.00 at 6 months, 1.73 at 1 year, and 1.32 at 2 years after trabeculectomy, respectively.

Summing up, they write: “Our results suggest that having cataract surgery after trabeculectomy does increase the risk of trabeculectomy failure and that the earlier that cataract surgery is performed, the greater the risk of failure.”

Reference:Cataract Surgery After Trabeculectomy

Arch Ophthalmol 2011.