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The authors of the article “Surgery for glaucoma in the 21st century”1 should be commended for attempting to tackle this issue. Nevertheless, we do feel that their fundamental points and principal arguments merit reconsideration.
The authors state categorically that “This finding of a higher ‘failure’ rate based on intraocular pressure after ‘non-penetrating’ surgery compared with trabeculectomy has been a finding in the majority of randomised trials comparing the two procedures” and then go on to quote three references allegedly supporting this remark.
One of the three studies2 reports lower mean IOP with deep sclerectomy compared to trabeculectomy (although not statistically significant) and almost identical success rates. What was significant was the dramatically lower complication rates with deep sclerectomy.
When discussing the other two papers3,4 it is of paramount importance to understand that given the long learning curve associated with deep sclerectomy, it is neither fair nor scientifically sound to compare a surgeon’s last 20 cases of trabeculectomy with his first 20 cases of deep sclerectomy. As an example, one group4 reported 0% success rate in their first series of viscocanalostomy patients and then presented their second series with a success rate of 15%.4 The same group also analysed the depth of their dissection of the deep sclera6 to find that they dissected too superficially in 48% of their cases and too deeply in 17%; meaning that the proper depth of dissection, which should bisect transversally the Schlemm’s canal deroofing it, was not achieved in the majority of their cases.
The authors also failed to cite published long term (43.2 (SD 14.3) months) results for deep sclerectomy with collagen implant.7 The study provided a qualified success rate of 94.8% and the complete success rate, 61.9% after 60 months (survival analysis), with a mean IOP at end of follow up of 11.8 (SD 3) mm Hg. Although the study reports a non-randomised consecutive series of patient, it should be taken as a proper indication of results achieved by experienced surgeons.
It should be taken into consideration that non-penetrating surgery is a broad genre of surgery, under which different surgeons perform fundamentally different procedures that include sinusotomy, ab externo trabeculectomy, deep sclerectomy with or without the use of an implant, viscocanalostomy, performance of postoperative goniopuncture, and the use of antimetabolites. The different techniques have one thing in common, the element of non-perforation.
What is true is that this type of surgery is continuously evolving, so it is unlikely that a proper judgment can be made yet. At the risk of sounding dramatic, it is valid to say that editorials like the one by Khaw et al seem to indirectly sign a death certificate of non-penetrating surgery. It is much more useful to encourage research in non-penetrating surgery, including multicentre randomised studies, to see if trabeculectomy will remain king.
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