Chapter 1
Introduction: a brief history of GATT
Ronald L. Fellman, Davinder S. Grover
Video 1
Two-site ab externo 360° suture trabeculotomy performed in an infant eye in1986 by Lynn and Fellman of Glaucoma Associates of Texas, Dallas, TX, USA. A metal trabeculotome did not fit the curvature of the eye. Instead, the on-the-spot idea of using a 6-0 prolene suture, modified from the 1960s filamentary trabeculotomy concept developed by England’s Redmond Smith, was used to successfully circumnavigate the canal in two 180° arcs. The inferior flap was made because the suture stopped at that location and a second flap was made to retrieve the blunted end to carry out the two 180° arc bowstring trabeculotomies, thus completing 360° in one setting. From a historical note, an inferior scleral flap was a typical approach for a second metal trabeculotomy in an infant eye when the first ab externo metal trabeculotomy failed to lower the intraocular pressure. Thus, it was a natural step to make an inferior scleral flap cutdown.
Video 2A & B
Development of single flap ab externo 360° suture trabeculotomy. The knowledge and skill required to perform an ab externo circumferential trabeculotomy, the most difficult of all ab externo anterior segment glaucoma surgeries, is paramount to every surgeon who specializes in childhood glaucomas. This essential skill may be necessary when the cornea is too hazy to safely perform an ab interno circumferential trabeculotomy. (a) After fashioning a scleral flap approximately 75% in thickness and a cutdown over the canal, the suture is inserted carefully into the canal. (b) After circumnavigating the canal for 360°, needle holders are used to grasp the ends of the suture, pulling in opposite directions, which bowstrings the suture through the inner wall of the canal, opening it for 360°.
Video 3
Intraoperative gonioscopy of Schlemm’s canal immediately after circumferential trabeculotomy. Note the white circumferential arc seen through the gonioprism. This represents the back wall of the canal, which becomes visible after the trabecular meshwork and inner wall of Schlemm’s canal have been cleaved open by the suture.
Video 4
First ab interno circumferential trabeculotomy attempt in 2011. This video is further explained Figure 4 in Chapter 1. This young construction worker had a failed Trabectome procedure, and the surgical idea, the genesis of GATT, was to perform the suture trabeculotomy through an ab interno approach, accessing through the Trabectome site, not ab externo. The surgeon (RLF) failed to circumnavigate the canal and switched over to the ab externo approach with the iTrack. The specifics of how to improve the surgery were further brainstormed at Glaucoma Associates of Texas, leading to the development of GATT.
Video 5
First GATT with iTrack illuminated microcatheter. This 18-year-old with juvenile glaucoma and uncontrolled intraocular pressure on maximal medications underwent the first GATT using the iTrack illuminated microcatheter in October 2011.
Video 6
Suture GATT. The suture GATT, a more affordable method to cleave open the canal, was a logical extension of the illuminated microcatheter. Success of the highly affordable suture allowed many health care systems around the globe to access GATT.