Laboratory Science: Original StudiesHistologic Findings of Trabecular Meshwork and Schlemm’s Canal After Microhook Ab Interno TrabeculotomyTsutsui, Aika MD*; Hamanaka, Teruhiko MD, PhD†,‡; Manabe, Kaoru MD*; Kaidzu, Sachiko PhD*; Kumasaka, Toshio MD, PhD§; Tanito, Masaki MD, PhD*Author Information *Department of Ophthalmology, Shimane University Faculty of Medicine, Izumo †Department of Ophthalmology, Japanese Red Cross Hospital Medical Center §Department of Pathology, Japanese Red Cross Hospital Medical Center, Tokyo ‡Department of Ophthalmology, Ishida Eye Clinic, Joetsu, Japan Disclosure: The microhooks used were co-developed by M.T., and Inami & Co., Ltd, Tokyo, Japan, and provided by Inami & Co., Ltd. M.T. receives royalties from Inami & Co., Ltd. The remaining authors declare no conflict of interest. Reprints: Masaki Tanito, MD, PhD, Department of Ophthalmology, Shimane University Faculty of Medicine, 89-1 Enya, Izumo, Shimane 693-8501, Japan (e-mail: [email protected]). Journal of Glaucoma: February 2021 - Volume 30 - Issue 2 - p 203-205 doi: 10.1097/IJG.0000000000001704 Buy Metrics Abstract Introduction: Trabeculotomy (LOT) and related goniotomy surgeries are classified based on excision or incision of the trabecular meshwork (TM); however, histologic evidence of the incision/excision pattern is insufficient. Case Presentations: Two cases of glaucomatous eyes in which trabeculectomy specimens previously “incised” during LOT were assessed histologically. A 39-year-old man with juvenile open-angle glaucoma (case 1) and a 70-year-old man with exfoliation glaucoma (case 2) underwent trabeculectomy for insufficient intraocular pressure reduction or visual field progression after initial microhook ab interno trabeculotomy (μLOT). In case 1, Schlemm’s canal (SC) opened into the anterior chamber due to extensive absence of the inner wall of SC and TM. In case 2, SC endothelium (SCE)-marker CD34 staining showed the slit-like entry site of a previous LOT, the SC lumen was sealed partially by scleral tissue, and CD34-positive and CD34-negative areas in the SC wall suggested SCE dropout and partial conversion of SC into ghost vessels. Active aqueous outflow-marker podoplanin (D2-40) staining showed intense immunolabeling in the sclera between the entry site and collector channels, indicating aqueous outflow. Discussion: The μLOT cleft can appear as both incisional and excisional patterns. In addition to incremental conventional outflow with reduced TM resistance, another unconventional outflow may be a mechanism of IOP reduction after LOT procedures. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.