Fig. 18.1
Superficial scleral flap, note that no diathermy is performed on episcleral vessels
Fig. 18.2
Superficial scleral flap sculpture with mini-Crescent knife
Fig. 18.3
Superficial scleral flap dissection in clear cornea
Right behind this, the Schlemm Canal is opened and exposed. The surgeon must take care to cut the Schlemm Canal ostias because it is believed that this will reduce the IOP to very low levels. This maneuver reduces the risk of perforating the trabeculo-Descemet membrane. The dissection must expose a small segment of the Descemet membrane, creating a trabeculo-Descemet window measuring approximately 1–1.5 mm. The corneal stroma can be separated from the Descemet membrane using a sponge, while the edges of the deep scleral flap are cut towards the cornea with a knife. In some cases there is tighter adhesion of the Descemet to the stroma and in these cases the surgeon can use a blunt spatula or a half-moon crescent knife with a brushing movement parallel to the limbus, to release these adhesions. This is a difficult phase of the procedure because there is a high risk of perforating the anterior chamber. The deep sclero-corneal flap is then removed by cutting it in clear cornea with small, delicate, extremely sharp scissors (for example, Vannas or Galand scissors). Then, the surgeon performs the so-called canaloplasty with the help of a microcatheter. This procedure should overcome some of the problems associated with the previous procedures that exploited a deep sclerectomy. The idea is to position a thin tension suture in the Schlemm Canal:
to expand internal space of the canal for the full 360°;
to expand the intertrabecular spaces;
to prevent the collapse of the canal, the surgical opening and the Descemet window, and the collapse of the internal wall into the holes of the collector canals;
to keep the Schlemm canal open;
to keep the collector canals used for drainage distant from the surgical site.
Fig. 18.4
Deep scleral flap sculpture with mini-Crescent knife; note the smaller size of the deeper flap
Fig. 18.5
Schlemm’s canal opening; note the different colour of the scleral bed, which indicates the adequate depth
Fig. 18.6
Descemet window enlargement to obtain the best exposition of the trabeculo-descemetic membrane; note the humour aqueous percolation, without membrane perforation; iris is visible thought the intact membrane
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