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27-08-2012 | Internal medicine | Article

Glaucoma microsurgery successful for IOP reduction, learning curve revealed


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medwireNews: Viscocanalostomy can successfully reduce intraocular pressure (IOP), significantly so at 1 week after surgery, in patients with open-angle glaucoma, report Swiss researchers.

Furthermore, their results indicate that the nonpenetrating filtration procedure, which has a "notorious learning curve," showed a significant improvement in success over a 4-year period, but that individual surgeon success rates stabilized after the 40th consecutive case.

"As expected in clinical practice, a time-related period is required to master any given surgical procedure, which is particularly true for microsurgical procedures such as viscocanalostomy," say Gordana Sunaric-Megevand (Clinique General Beaulieu, Geneva) and colleagues.

They add that avoiding full-thickness penetration into the anterior chamber during glaucoma surgery can minimize the risk for vision-threatening complications postsurgery.

Indeed, trabeculo-Descemet membrane (TDM) perforation - an indicator of surgical performance - decreased from 20% in the first 45 surgical cases in the study to just 2% in the last 45 cases.

The researchers reviewed a total of 180 viscocanalostomy procedures undertaken by two surgeons between 1996 and 2000, and after a median 28-month follow up, found significant improvements in the rates of overall and complete success.

Overall success, defined as no visual field deterioration after surgery, a postoperative IOP of 20 mmHg or below, and an IOP reduction of at least 30% compared with baseline with or without medication, improved from 64% to 91% comparing the first and last 45 surgical cases.

Complete success, defined as overall success that required no further postsurgery medication, improved from 38% to 73% over the same period.

Mean preoperative IOP decreased from 24 mmHg to 10 mmHg at 1 week, 13 mmHg at 1 month, and was 14 mmHg at 36 months after surgery, report Sunaric-Megevand et al.

After analyzing the surgeons' overall and complete success rates, no further significant improvement was observed after the 40th consecutive case.

"Clearly a learning curve exists for viscocanalostomy in which success rates improve and complication rates decrease as surgeons gain experience," the researchers conclude in the Journal of Glaucoma.

medwireNews ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2012

By Sarah Guy, medwireNews Reporter

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