Dietlein T. S.

Universitäts-Augenklinik Köln

Background: The key point of non-penetrating glaucoma surgery is the dissection of a deep scleral flap and the unroofing of Schlemm_s canal preserving the integrity of the trabecular meshwork. The exact mode of pressure-reduction is still obscure as well as the long-term efficacy compared to conventional trabeculectomy.
Methods: In a prospective randomized study 40 patients were enrolled either for viscocanalostomy or trabeculectomy. Light-microscopy of the deep scleral flap after viscocanalostomy was performed in more than 40 cases and of the trabeculectomy specimen in nearly 200 cases.
Results: Without secondary interventions the pressure-reducing efficacy of viscocanalostomy after 12 months was weaker than of trabeculectomy. Morphology of the deep scleral flap revealed a remarkable variability of the dissection level and thickness of the deep flap, even in experienced hands. Light-microscopy of the trabeculectomy specimens showed a very thin anterior meshwork, especially in old patients, a very weak pigmentation in the vaste majority and a lumen of Schlemm_s canal that is often hard to distinguish.
Discussion: Perioperative complications as well as functional efficacy of viscocanalstomy seem to be less pronounced than after trabeculectomy in our glaucoma population. From a morphological point of view, microruptures and partial resection of the inner meshwork may be the key to pressure reduction after non-penetrating surgery - at least in a certain percentage of cases.

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