ORIGINAL ARTICLE Ab Interno Trabeculectomy: Development of a Novel Device (Trabectome TM ) and Surgery for Open-Angle Glaucoma Brian A. Francis, MD,* Robert F. See, MD,† Narsing A. Rao, MD,* Don S. Minckler, MD,* and George Baerveldt, MD‡ Purpose: To design an instrument to selectively remove trabecular meshwork and Schlemm’s canal inner wall (SCIW), and demonstrate its effectiveness by histologic analysis of treated cadaveric human tissue. Methods: The design parameters of the instrument were the ability to permanently remove a segment of trabecular meshwork and Schlemm’s canal inner wall without causing damage to surrounding tissue, and to allow use with standard anterior segment surgical tech- niques and equipment via an ab interno approach. Treatment was applied to 20 segments of human corneoscleral rims. The treated areas were examined using a confocal microscope and compared with matching areas in untreated controls and simulated goniotomy. Results: The resultant instrument system surgically removes the trabecular meshwork and Schlemm’s canal inner wall from an anterior chamber approach. It consists of a disposable surgical handpiece with irrigation, aspiration, and electrocautery to focally ablate the target tissues. The attached console includes a high-frequency (550 KHz) electrosurgical generator and irrigation/aspiration controlled by a foot pedal. Histologic examination of specimens treated with the Trabectome TM displayed disruption of the trabecular meshwork and Schlemm’s canal inner wall without damage to surrounding struc- tures. The specimens treated by simulated goniotomy displayed signifi- cant damage to the outer wall of Schlemm’s canal and the surrounding sclera. The controls showed no disruption or damage to any tissues. Conclusions: The Trabectome TM system is designed for performing trabeculectomy via an ab interno approach. It successfully removed sections of trabecular meshwork and Schlemm’s canal inner wall with less injury to the adjacent tissue compared with goniotomy knife in vitro. Theoretically, this procedure should provide direct access of aqueous humor to Schlemm’s canal. Key Words: ab interno, glaucoma, gonio surgery, trabectome, trabeculectomy (J Glaucoma 2006;15:68–73) S urgical therapy for open-angle glaucoma can be divided into procedures directed at decreasing aqueous inflow or increasing outflow. The latter is more common, and can be further divided into external filtering procedures (such as trabeculectomy), and outflow surgeries that attempt to increase physiologic aqueous outflow through the angle pathway. Direct modification of the outflow pathway surgically is jus- tified by the hypothesis that the majority of outflow obstruc- tion in primary open-angle glaucoma (POAG) lies in the juxtacanalicular trabedular meshwork (TM) or inner wall of Schlemm’s canal (SC). 1,2 Examples of this approach are goniotomy, trabeculotomy, and other mechanical disruptions of the trabecular meshwork, such as trabeculopuncture, 3 goniophotoablation, laser trabecular ablation, trabecular aspiration, 4,5 and goniocurretage. 6 Goniotomy and trabeculotomy have attained success rates of 65% and greater in congenital glaucomas. 7–9 However, despite an initial favorable response in the treatment of open- angle glaucoma, utilizing goniotomy or trabeculotomy long- term review of surgical results showed only limited success in adults. 10,11 In retrospect, these procedures may have failed due to cellular repair and fibrosis mechanisms and a process of ‘‘filling in’’ of the clefts created surgically. Goniocurretage, also performed via gonioscopic lenses, is designed to mechanically disrupt and remove segments of trabecular meshwork using a spoon-like instrument. The ÔgonioscraperÕ consists of a small handle and a slightly convex- shaped arm for intraocular use and resembles a cyclodialysis spatula. The tip of the instrument is shaped as a tiny bowl 300 mm diameter and with its edges sharpened. Analysis of this procedure indicates that, in addition to a complete disruption of the trabecular meshwork and internal wall of Schlemm’s canal, it may also cause damage to intracanalicular septae and splitting along the posterior wall of Schlemm’s canal. Received for publication June 28, 2005; Accepted August 30, 2005. From the *Doheny Eye Institute, Keck School of Medicine, University of Southern California; Los Angeles, California; †Duke University Eye Center, Duke University Medical Center, Durham, North Carolina; ‡Department of Ophthalmology, University of California, Irvine; Irvine, California. This work was supported in part by National Institutes of Health core Grant EY03040 and by an unrestricted grant from Research to Prevent Blindness, New York, NY. Robert F. See, MD, has been a paid consultant for Neomedix Corporation. He has no continuing financial interest in the company or its technology. George Baerveldt, MD, is the inventor of the Trabectome TM and is a consultant for NeoMedix. Reprints: Brian A. Francis, University of Southern California/Doheny Eye Institute, 1450 San Pablo Street—DEI 4804, Los Angeles, CA 90033 (e-mail: bfrancis@usc.edu). Copyright Ó 2006 by Lippincott Williams & Wilkins 68 J Glaucoma  Volume 15, Number 1, February 2006 Copyright ' Lippincott Williams & Wilkins. 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