Surgical Outcomes of Prolene Gonioscopy-assisted Transluminal Trabeculotomy in Patients With Moderate to Advanced Open-Angle Glaucoma Zeynep Aktas, MD, FEBO,* Ahmet Y. Ucgul, MD,† Caglar Bektas, MD,* and Selin Sahin Karamert, MD* Précis: The present study demonstrates that surgical success rate of gonioscopy-assisted transluminal trabeculotomy (GATT) is 83.7% according to target intraocular pressure (IOP) ≤ 21 mm Hg and ≥ 20% reduction from baseline in patients with moderate to advanced glaucoma, with an average follow-up of 19.4 months. Purpose: The aim of the study was to assess the outcomes of GATT in eyes with moderate to advanced open-angle glaucoma. Patients and Methods: A retrospective study included 104 eyes of 104 patients, with a mean age of 58.9 ± 18.5 (15 to 87) years, who underwent GATT using the 6/0 prolene suture to treat open-angle glaucoma. The GATT procedure was carried out alone or in combination with phacoemulsification. IOP at baseline, third, sixth, ninth, 12th, and 18th months of follow-up; need of antiglaucoma medication; need of further glaucoma surgery; cup/disc ratio; and best-corrected visual acuity (BCVA) were recorded. Patients with prior incisional glaucoma surgery were excluded. Surgical success was determined for both IOP <21 and <18 mm Hg and also ≥ 20% reduction from baseline without further glaucoma surgery. Results: A total of 65 patients with primary open-angle glaucoma (POAG) and 39 patients with secondary open-angle glaucoma (SOAG), including pseudoexfoliative, pigmentary, uveitic, and ste- roid-induced glaucoma underwent GATT. Preoperative mean IOP was 25.0 ± 7.3 mm Hg. Preoperative average number of anti- glaucoma medications was 3.4 ± 0.6. The average follow-up time was 19.4 ± 8.1 (6 to 37) months. Preoperative average BCVA was 0.51 ± 0.24, and cup/disc ratio was 0.85 ± 0.14. Surgical success was achieved in 87 of 104 (83.7%). Seven patients had medically uncontrolled glaucoma after GATT surgery, and they underwent further surgery. Patients with POAG had a higher percentage of IOP reduction than patients with SOAG at 18th month of follow-up (40.1% vs. 27.6%). Need for medication at final visit was similar between POAG and SOAG. Conclusion: GATT procedure is a safe and successful option for the treatment of moderate to advanced open-angle glaucoma. Surgical success could be maintained up to ∼18 months. Key Words: advanced glaucoma, GATT, gonioscopy-assisted transluminal trabeculotomy, moderate glaucoma, open-angle glaucoma (J Glaucoma 2019;28:884–888) T rabeculectomy is still the most frequently performed glaucoma surgery around the world. 1 However, in recent years, microinvasive glaucoma surgery (MIGS) has been extremely popular because of its safer surgical profile. On the contrary, trabeculectomy has considerable numerous vision-threatening complications, such as hypotonia, cho- roidal effusion, or endophthalmitis. 2 This explains why glaucoma surgeons tend to perform MIGS, which has more favorable safety profile. MIGS could be simply performed with cataract surgery and is usually preferred in mild to moderate glaucoma cases. 3 Bypassing or removing unfunctional trabecular mesh- work (TM) with MIGS targeting Schlemm canal (SC) results in improved outflow pathway. Gonioscopy-assisted transluminal trabeculotomy (GATT) procedure is an MIGS technique, first described by Grover et al, 4–7 in which the TM is circumferentially bypassed using a prolene suture or catheter. GATT procedure provides aqueous humor to reach collector channels and episcleral veins through the circumferentially torn and opened unfunctional TM. Herein, we aimed to evaluate the efficiency of prolene- GATT surgery in patients with moderate to advanced open- angle glaucoma. PATIENTS AND METHODS This retrospective comparative study was approved by the Gazi University Ethical Committee and Review Board and was conducted in accordance with the declaration of Helsinki. Patients Patients with open-angle glaucoma undergoing GATT surgery were retrospectively analyzed. Preoperative gonio- scopy was performed with goniolens in all eyes to check the visibility of angle landmarks, particularly TM. Patients with open-angle glaucoma with uncontrolled intraocular pressure (IOP) despite maximum medical therapy, patients with the evidence of glaucoma progression in retinal nerve fiber layer and visual field tests, or patients who could not have tol- erated medical therapy were included into study, and GATT surgery was performed in those eyes. Therefore, the lower limit of preoperative IOP for GATT surgery was not defined. Patients who underwent <360-degree trabeculot- omy and patients with chronic angle-closure, neovascular glaucoma, unidentifiable TM, corneal decompensation, DOI: 10.1097/IJG.0000000000001331 Received for publication February 26, 2019; accepted July 14, 2019. From the *Department of Ophthalmology, Gazi University School of Medicine, Ankara; and †Department of Ophthalmology, Abant Izzet Baysal University, Training and Research Hospital, Bolu, Turkey. Disclosure: The authors declare no conflict of interest. Reprints: Zeynep Aktas, MD, FEBO, 172. Sok Bahcelievler mah, Safak Sitesi No: 4, Golbasi-Ankara 06830, Turkey (e-mail: drzeynep2000@ yahoo.com). Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website, www. glaucomajournal.com. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved. ORIGINAL STUDY 884 | www.glaucomajournal.com J Glaucoma  Volume 28, Number 10, October 2019 Copyright r 2019 Wolters Kluwer Health, Inc. All rights reserved.