Viscocanalostomy vs. Trabeculectomy

Abstract

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,1Nonpenetrating glaucoma surgery. American Academy of Ophthalmology.Ophthalmology. 2001; 108: 416-421Abstract Full Text Full Text PDF PubMed Scopus (45) Google Scholar 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 Ophthalmology2Rothman R.F. Liebmann J.M. Ritch R. Low dose 5-Fluoruracile trabeculectomy as initial surgery in uncomplicated glaucoma long term followup.Ophthalmology. 2000; 107: 1184-1190Abstract Full Text Full Text PDF PubMed Scopus (53) Google Scholar reports a success rate (Kaplan-Meier, IOP ≤21 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,3Diestelhorst M. Khalili M.A. Krieglstein G.K. Trabeculectomy a retrospective follow-up of 700 eyes.Int Ophthalmol. 1999; 22: 211-220Crossref Scopus (29) Google Scholar 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 conducting more than 120 viscocanalostomies, as reported in the Discussion. 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,1Nonpenetrating glaucoma surgery. American Academy of Ophthalmology.Ophthalmology. 2001; 108: 416-421Abstract Full Text Full Text PDF PubMed Scopus (45) Google Scholar 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 Ophthalmology2Rothman R.F. Liebmann J.M. Ritch R. Low dose 5-Fluoruracile trabeculectomy as initial surgery in uncomplicated glaucoma long term followup.Ophthalmology. 2000; 107: 1184-1190Abstract Full Text Full Text PDF PubMed Scopus (53) Google Scholar reports a success rate (Kaplan-Meier, IOP ≤21 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,3Diestelhorst M. Khalili M.A. Krieglstein G.K. Trabeculectomy a retrospective follow-up of 700 eyes.Int Ophthalmol. 1999; 22: 211-220Crossref Scopus (29) Google Scholar 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 conducting more than 120 viscocanalostomies, as reported in the Discussion. Viscocanalostomy vs. Trabeculectomy: Author replyOphthalmologyVol. 109Issue 3Preview Full-Text PDF