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• Re: Non-penetrating gluacoma surgery
  Roger A Hitchings
  Published on: 25 March 2003
• Non-penetrating gluacoma surgery
  Tarek M Shaarawy
  Published on: 20 November 2002

• Published on: 25 March 2003

  Re: Non-penetrating gluacoma surgery

  • Roger A Hitchings, Ophthalmologist

  Dear Editor

  We thank Drs Sharawary and Mermoud for their interest in our article [1] and respect their observations. They have made significant contributions to our understanding of non penetrating surgery in the treatment of chronic open angle glaucoma.

  With any new surgical technique information changes rapidly, and much new information has appeared since our article was written. The authors note current li...

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  Dear Editor

  We thank Drs Sharawary and Mermoud for their interest in our article [1] and respect their observations. They have made significant contributions to our understanding of non penetrating surgery in the treatment of chronic open angle glaucoma.

  With any new surgical technique information changes rapidly, and much new information has appeared since our article was written. The authors note current literature as well as the effects of 'the learning curve' that might affect results. The point of our article was to summarise the then position and suggest outcome measures to note for the future. As chronic glaucoma is a very long term disease even medium term results can only give at best give an indication of the visual outcome of treatment. Our current knowledge of treatment for these glaucoma's strongly suggests that the lower the intraocular pressure within the statistically normal range the better. The evidence to date still suggests that there is a greater likelyhood of these lower intraocular pressures being achieved by 'penetrating' rather then 'non penetrating' surgery. This needs to be taken into account when advising the patient on which surgical approach would be in their best interest.

  Roger Hitchings

  Reference

  (1) Tan JCH, Hitchings RA. Non-penetrating glaucoma surgery: the state of play. Br J Ophthalmol 2001;85: 234-237.

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  Conflict of Interest:
  None declared.

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• Published on: 20 November 2002

  Non-penetrating gluacoma surgery

  • Tarek M Shaarawy, Head, Glaucoma Unit
  • Other Contributors:
    • Andre Mermoud, MD

  Dear Editor

  The authors of this article (Tan J C H, and Hitchings R. Non-penetrating glaucoma surgery: the state of play. Br J Ophthalmol 2001;85:234-237) should be commended on attempting to tackle this issue. Nevertheless we do feel that their fundamental points and principal arguments merit reconsideration.

  The authors state categorically that "long term outcomes do not exit for the newer...

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  Dear Editor

  The authors of this article (Tan J C H, and Hitchings R. Non-penetrating glaucoma surgery: the state of play. Br J Ophthalmol 2001;85:234-237) should be commended on attempting to tackle this issue. Nevertheless we do feel that their fundamental points and principal arguments merit reconsideration.

  The authors state categorically that "long term outcomes do not exit for the newer non-penetrating surgery technique" when in fact long term (43.2 months +/- 14.3 (SD)) results for deep sclerectomy with collagen implant have been presented to the European Glaucoma Society (EGS) Glaucoma Symposium, 2000, and have also been published some time ago.[1] 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 +/- 3. The study reported no surgically induced cataract of the whole series of 105 patients.

  The authors, unfortunately, failed to cite a landmark study[2] comparing deep sclerectomy without an implant to trabeculectomy in the two eyes of the same patient in a prospective randomised fashion. At 12 months, mean IOP reduction was 12.3 +/- 4.2 (sclerectomy) versus 14.1 +/- 6.4 mmHg (trabeculectomy) (P = 0.15), and an IOP Furthermore the authors cite a study by Gandolfi as personal communication supposedly providing evidence that "trabeculectomy produces lower and better sustained IOP control than either viscocanalostomy or deep sclerectomy". The authors fail to mention however, that in this particular study postoperative YAG goniopunctures were considered as a failure criteria. Excluding goniopuncture from the success criteria would easily be compared to considering laser suture lysis or even YAG capsulotomies to be failure criteria of glaucoma or cataract surgeries. Furthermore Gandolfi concluded that Deep sclerectomy was associated with lower perturbation of lens nuclear transparency (personal communication, January 2002).

  In another point worthy of reconsideration the authors site a study [3] that allegedly draws attention to high rates of hypotony and hyphaema after intraoperative conversion of deep sclerectomy to trabeculectomy following accidental intraopeartive perforation of the trabeculo- Descemet's membrane (TDM). However the authors again fail to mention, when quoting this specific study, that "when deep sclerectomy is complicated with a perforation of the TDM, the long term success rate of the surgery is similar to that of trabeculectomy". This conclusion would encourage the surgeons to start their surgery as a deep sclerectomy, knowing that in case of a perforation and a subsequent transformation to trabeculectomy, the chances of success would be similar to initial trabeculectomy.

  The authors of the paper at hand compare in their figures viscocanalostomy, deep scelerectomy without an implant, deep sclerectomy with collagen implant, and deep sclerectomy without suturing the superficial flap to each other, and thus drawing certain conclusions. The different techniques have one thing in common, the element of non- perforation. It is not useful to compare apples and pears.

  A major factor in the conflicting, often contradictory, results available is the element of long learning curves. As an example one group reported 0% success rate in their first series of viscocanalostomy patients [4] and then presented their second series with a success rate of 15%.[5]

  The same group also analyzed the depth of their dissection of the deep sclera [6] 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.

  To achieve successful non-penetrating surgery, the dissection of the deep sclerectomy needs to be correct. This entails a total excision of corneal stroma behind Descemet's membrane and the excision of the inner wall of Schlemm's canal and the juxtacanalicular trabeculum. An implant has to be used to maintain the scleral space patent.[7] Laser goniopuncture should be performed at any postoperative stage when IOP mounts beyond the target pressure. We do however wholeheartedly agree with the authors on the importance of conducting a large-scale multinational randomised prospective trial as the only possible method to compare non-penetrating glaucoma surgery, or any other new surgical practice, to trabeculectomy.

  Tarek Shaarawy¹, MD and André Mermoud², MD

  1. Head Glaucoma unit, Memorial Research Institute of Ophthalmology, Giza, Egypt.
  2. Head Glaucoma unit, University of Lausanne, Switzerland.

  References

  (1) Shaarawy T, Karlen M, Schnyder C, Achache F, Sanchez E, Mermoud A. Five-year results of deep sclerectomy with collagen implant. J Cataract Refract Surg 2001;27:1770-8.

  (2) El Sayyad F, Helal M, El Kholify H, Khalil M, El Maghraby A. Nonpenetrating deep sclerectomy versus trabeculectomy in bilateral primary open-angle glaucoma. Ophthalmology 2000;107:1671-4.

  (3) Sanchez E, Schnyder CC, Mermoud A. [Comparative results of deep sclerectomy transformed to trabeculectomy and classical trabeculectomy]. Klin Monatsbl Augenheilkd 1997;210:261-4.

  (4) Jonescu-Cuypers C, Jacobi P, Konen W, Krieglstein G. Primary viscocanalostomy versus trabeculectomy in white patients with open-angle glaucoma: A randomized clinical trial. Ophthalmology 2001;108:254-8.

  (5) Dietlein, T. S. and Krieglstein, G. K. Morphology and pressure- reducing efficacy after viscocanalostomy. 23. 2001. Paris, European Glaucoma Society. Closed Meeting of the European Glaucoma Society.

  (6) Dietlein TS, Luke C, Jacobi PC, Konen W, Krieglstein GK. Variability of dissection depth in deep sclerectomy: morphological analysis of the deep scleral flap. Graefes Arch Clin Exp Ophthalmol 2000;238:405-9.

  (7) Shaarawy, T., Nguyen Chr, Schnyder, C., Achache, F., and Mermoud, A. Comparative study between deep sclerectomy with and without collagen implant: Long term follow-up. Invest Ophthalmol42(4), S544. 2001.

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  Conflict of Interest:
  None declared.

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