Enormous progress has been made in understanding the complexity of the underlying causes of chronic open-angle glaucoma; however, indisputable concepts for effective treatment are still rare. To date, conventional filtering surgery remains the mainstay of surgical therapy in the management of glaucoma not controlled by medication.<sup>25 Jay J.L., Murray S.B. Early trabeculectomy versus conventional management in primary open angle glaucoma Br J Ophthalmol 1998 ;  72 : 881-889

Cliquez ici pour aller à la section Références</sup> Unfortunately, treatments involving full-thickness filtration are scarcely selective, as healthy structures not primarily involved in the disease process are subject to surgical intervention. The application of adjunct antimetabolites for inhibition of undesired episcleral fibroblastic proliferation dramatically increased the success rates for filtering procedures but had the disadvantage of exacerbating serious side effects, such as flat anterior chambers, prolonged postoperative hypotony, and late endophthalmitis from infected filtering blebs.<sup>27 Kitazawa Y., Yamamoto T. The risk profile of mitomycin C in glaucoma surgery Curr Opinion Ophthalmol 1994 ;  5 : 105-109  [cross-ref]

Cliquez ici pour aller à la section Références, 45 Stamper R.L., McMenemy M.G., Liebermann M.F. Hypotonous maculopathy after trabeculectomy with subconjunctival 5-fluorouracil Am J Ophthalmol 1992 ;  114 : 553-554

Cliquez ici pour aller à la section Références</sup>

Microsurgery on Schlemm's canal and the human aqueous outflow system for controlling intraocular pressure (IOP) in chronic open-angle glaucoma have been evolving over the past few decades. Theoretic considerations indicate that production of approximately 10 to 15 fistulae, each 10 μm in diameter, between the anterior chamber and Schlemm's canal should restore normal outflow facility in open-angle glaucoma.<sup>9 Goldschmidt C.R., Ticho U. Theoretical approach to laser trabeculotomy Med Phys 1978 ;  5 : 92-98  [cross-ref]

Cliquez ici pour aller à la section Références</sup> The basis for most of the current approaches to microsurgery of Schlemm's canal is the finding by Grant<sup>10 Grant W.M. Further studies on facility of flow through the trabecular meshwork Arch Ophthalmol 1958 ;  60 : 523-533

Cliquez ici pour aller à la section Références</sup> that the largest proportion of resistance to outflow is located within the trabecular meshwork, namely, the cribriform layer and can be eliminated by incising the trabecular meshwork and entering the canal of Schlemm. If one agrees that the site of the pathologic resistance to aqueous humor outflow is this tissue, then partial removal, taking the utmost possible care not to damage the surrounding chamber angle structures, could be a new alternative in antiglaucomatous surgery. This sort of selective nonpenetrating trabecular surgery would be equivalent to internal filtration surgery without transscleral drainage of aqueous humor into the subconjuntival space and would thereby reduce the incidence of postoperative complications typically associated with filtering procedures.

This review discusses different internal trabecular microsurgical techniques that are designed to facilitate outflow along its natural pathway. Each new technique is described in detail, newly developed instrumentation is discussed, and the presumed mechanisms of action are outlined. The reader must understand, however, that none of these new microsurgical procedures threaten to replace conventional filtering approaches, as they are still in the experimental phase and under careful clinical evaluation, and there is plenty of room left for further refinements and developments. We hope this article gives us impetus to the search for alternative strategies in antiglaucomatous surgery and focuses attention more closely on the diseased target structure in chronic open-angle glaucoma: the trabecular meshwork.