Viscocanalostomy vs. Trabeculectomy1

Ophthalmology Volume 109, Number 3, March 2002 Viscocanalostomy vs. Trabeculectomy The following two letters address an article that appeared in the February issue of the Journal: Jonescu-Cuypers CP, Jacob PC, Konen W, Krieglstein GK. Primary Viscocanalostomy Versus Trabeculectomy in White Patients with Open-Angle Glaucoma: A Randomized Clinical Trial. (Ophthalmology 2001; 108:254 – 8) Dear Editor: Jonescu-Cuypers et al recently reported the first controlled randomized clinical trial of viscocanalostomy vs. trabeculectomy in medically uncontrolled primary open-angle glaucoma (POAG). We wish to congratulate the authors for proposing a study meant to clarify the role of nonpenetrating surgery, which has rapidly become one of the most debated issues in the field of glaucoma. After comparing the outcome and the complications of the two procedures, the authors concluded that success, defined as an intraoccular pressure (IOP) of ⬍20 mmHg without additional surgery or medication, was 50% in trabeculectomy and 0% in viscocanalostomy only 6 months after surgery. We think that these results should be considered with caution, being so peculiarly different from literature data and may be due to a limited sample size. In fact, according to the review of nonpenetrating glaucoma surgery by the American Academy of Ophthalmology Ophthalmic Technology Assessment,1 all the studies published until now indicate that viscocanalostomy has an IOP-lowering effect, with postoperative IOPs generally in the high-normal range, and with variable, but certainly nonzero, degrees of success. In our experience, at 24 months, the Kaplan-Meier probability of survival between 6 and 21 mmHg was 76%, whereas only 46% of the operated eyes achieved an IOP ⬍16 mmHg (oral presentation at the American Academy of Ophthalmology Glaucoma Subspeciality Day, Dallas, Texas, October 21, 2000). Regardless of any consideration about viscocanalostomy, even trabeculectomy seems to yield an overly unfavorable outcome in Jonescu-Cuypers’ study, considering that the eyes included (POAG; mean age, 62.5 years, with no history of ocular surgery) were typically at low risk of failure of conventional penetrating surgery. For instance, among several others, an article recently published in Ophthalmology2 reports a success rate (Kaplan-Meier, IOP ⱕ21 mmHg on no medication) of 87.1% and 51.3% at 1 and 5 years, respectively, after trabeculectomy with no antimetabolites. Moreover, according to an exhaustive overview of 700 eyes,3 the success of trabeculectomy in the authors’ clinic was 48.6% after a mean follow-up of 16.3 months. The authors themselves state in the Discussion that their personal standard success rate of trabeculectomy is 80% at 6 months. Undoubtedly, viscocanolostomy is a difficult procedure, and a very precise technique is mandatory to achieve success. We certainly believe that the authors, who are highly trained in glaucoma surgery, must have recorded more encouraging results for nonpenetrating surgery in their previous experience to motivate their perseverance in conduct-

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ing more than 120 viscocanalostomies, as reported in the Discussion. ROBERTO G. CARASSA, MD PAOLO BETTIN, MD ROSARIO BRANCATO, MD Milano, Italy Reference 1. Nonpenetrating glaucoma surgery. American Academy of Ophthalmology. Ophthalmology 2001;108:416 –21 2. Rothman RF, Liebmann JM, Ritch R: Low dose 5-Fluoruracile trabeculectomy as initial surgery in uncomplicated glaucoma: long term followup. Ophthalmology 2000;107:1184 –90. 3. Diestelhorst M, Khalili MA, Krieglstein GK: Trabeculectomy: a retrospective follow-up of 700 eyes. Int Ophthalmol 1999;22: 211–20.

Author reply Dear Editor: We agree with Drs. Carassa, Bettin, and Brancato that the study, both with respect to sample size and follow-up time, is not adeqate to describe the therapeutic profile of viscocanalostomy. However, the study was not designed to accomplish that. The goal of the study was to compare the intraocular pressure (IOP)–lowering potency of viscocanalostomy with traditional trabeculectomy using the best possible screening techniques. Inclusion, endpoint, and criteria of complete success were defined in a most stringent way. We tried to substantiate the comparative IOP–lowering potential of both procedures, considering the surgical intervention solely. No IOP-effective medication, no additional surgical adjuncts (i.e., laser goniopuncture, laser suturelysis, digital massage, antimetabolite injection) were allowed in either group. IOP in the operated eye that increased to 21 mmHg or greater on any of the postoperative visits was considered as endpoint and failure. In many of the cases, after analyses of nonperforating glaucoma surgery, “complete success” was defined as IOP less than a certain level without glaucoma medications; however, minisurgical maneuvers of various kinds were used postoperatively in most patients. If the study design of Carassa et al had been narrowed to our criteria, the outcome might have been the same. Carassa et al note that we have performed more than 120 viscocanalostomies, yet published findings on a small series. We made sure to allow adequate time and opportunity to complete the learning curve, and after disappointing clinical experience, we decided on a “hard test” for the procedure: IOP ⬍21 mmHg vs. failure without postoperative medications or any surgical adjuncts, in a randomized, prospective, controlled study design. The inferiority of nonperforating surgery compared with trabeculectomy was so marked that we thought publication, even of such a small study, would be worthwhile. Considering the low success rate of trabeculectomy in our study, the same arguments would be applicable. In an observational study of glaucoma treatment patterns over 2 years comprising nine countries of the industrialized world, 50% of all patients having undergone trabeculectomy were receiving IOP-lowering medication again within 3 months,