Fig. 17.1
First 300 mcr of thickness scleral flap sculpture , advancing the incision in clear cornea
Fig. 17.2
Second scleral flap sculpture and inner Schlemm’s canal wall exposition; Descemet membrane is not exposed yet
Fig. 17.3
Paracentesis after Schlemm’s canal/trabecular meshwork exposition before Descemet window creation made to reduce pressure on a very thin and fragile tissue. In this way we reduce the risk of undesired rupture
The most recently-developed non-penetrating procedures do not open the Descemet membrane or the trabecular meshwork, but they allow the natural resistance of the tissues to oppose the fluid outflow. The deep sclerectomy involves the creation of two scleral flaps, the removal of the deep flap (deep sclerectomy) leaving the intact descemet membrane and trabecular meshwork and descemet membrane the trabeculate and an aqueous intrascleral pool (often described as a scleral lake) exposed. The deep sclerectomy involves the preparation of two scleral flaps—one superficial and one deep. The superficial flap is usually 300 μm thick and it must be cut at least 1.0 mm in clear cornea. Preparation of the deep flap reveals the scleral spur lying parallel to the limbus, and the anterior blue zone within the limits of the Schwalbe line (rarely visible in Caucasian patients) The Schlemm Canal is found directly in front of the scleral spur. The trabeculate lies anterior to the scleral spur. The Trabecubecular Descemetic Membrane (TDM) extends anteriorly from the Schwalbe line for approximately 1 mm in clear cornea.
