**8. Non-Penetrating Glaucoma Surgery (NPGS)**

Non-penetrating glaucoma surgery (NPGS) is a filtration procedure in which the anterior chamber is not penetrated. [48]- [50] It is based on creation of a partial thickness scleral flap and a deep pocket in the area of the outer wall of the Schlemm's canal. It involves the Schlemm's canal without penetrating its inner wall. Three variations of the procedure exist: canaloplasty, viscocanalostomy and deep sclerostomy. In the first procedure, a 10-0 nylon is passed through the Schlemm's canal while in the second, viscoelastic agent such as hyalur‐ onic acid (Healon®) is injected into the canal. The aqueous flows through the trabeculo-De‐ scemet's membrane into scleral pocket and from there to surrounding blood and aqueous vessels. The NPGS with intraoperative MMC is promising showing good short-term (be‐ tween one and three years) success, but a long follow-up is required.
