Nonpenetrating Glaucoma Surgery
Nonpenetrating glaucoma procedures are incisional glaucoma surgeries that do not enter the anterior chamber; their goal is to lower IOP while avoiding some of the complications of trabeculectomy. These nonpenetrating procedures include deep sclerectomy, viscocanalostomy, and canaloplasty (Video 13-22). In both viscocanalostomy and canaloplasty, a deep sclerectomy is augmented with injection of viscoelastic into Schlemm canal. In viscocanalostomy, a cannula is used to inject viscoelastic into a limited section of Schlemm canal. In canaloplasty, a flexible illuminated catheter is utilized to inject viscoelastic into the full 360° of Schlemm canal and to pass a suture through it; the suture is then tied under moderate tension, leaving the canal stretched. For these 3 procedures, the surgeon creates a fornix-based conjunctival incision and then a superficial scleral flap. Deeper sclera and peripheral cornea are removed underneath this flap, leaving only a thin layer of sclera and Descemet membrane. This allows aqueous to percolate through Descemet membrane into a scleral lake formed by removal of the deep scleral flap.
Courtesy of Steven Vold, MD.
These surgeries are indicated for OAG. Currently, there are limited long-term data from prospective randomized trials comparing these newer procedures with trabeculectomy. Although nonpenetrating surgery may avoid some of the complications associated with trabeculectomy, they are technically challenging; and most results suggest that IOP reduction with these procedures is less than that obtained with trabeculectomy. They also cause conjunctival scarring, which may limit future surgical options. In addition, the surgeon may need to convert intraoperatively to trabeculectomy. Postoperative Nd:YAG laser goniopuncture of Descemet membrane may be needed to increase aqueous flow. Complications include Descemet detachment and infection.
Chai C, Loon SC. Meta-analysis of viscocanalostomy versus trabeculectomy in uncontrolled glaucoma. J Glaucoma. 2010;19(8):519–527.
Gilmour DF, Manners TD, Devonport H, Varga Z, Solebo AL, Miles J. Viscocanalostomy versus trabeculectomy for primary open angle glaucoma: 4-year prospective randomized clinical trial. Eye (Lond). 2009;23(9):1802–1807.
Lewis RA, von Wolff K, Tetz M, et al. Canaloplasty: circumferential viscodilation and tensioning of Schlemm canal using a flexible microcatheter for the treatment of open-angle glaucoma in adults: two-year interim clinical study results. J Cataract Refract Surg. 2009;35(5):814–824.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.