Gonioscopy-assisted transluminal trabeculotomy (GATT) has been shown to be successful in the management of both primary and secondary open-angle glaucoma. Patient selection and management of expectations is key.
By Dr Yasmine M. El Sayed
Gonioscopy-assisted transluminal trabeculotomy (GATT) is an ab interno, minimally invasive glaucoma surgery introduced by Dr Ronald Fellman in 2014.1 It aims to circumferentially incise the inner wall of Schlemm’s canal (SC), in order to connect it directly to the anterior chamber.
The procedure is performed through two clear corneal incisions, under gonioscopic view. An illuminated microcatheter or a prolene suture is introduced into SC through a goniotomy incision and threaded using 23 g microsurgical forceps, coursing circumferentially throughout the entire canal, until it reappears from the opposite cut end of SC. Both ends are then pulled out, creating a 360° incision, cleaving the entire trabecular meshwork (Figure 1).
GATT has been shown to be successful in the management of both primary and secondary open-angle glaucoma, particularly in steroid-induced glaucoma.2 It has also demonstrated effectiveness in paediatric glaucoma and in eyes with a history of previous incisional procedures, including trabeculectomy and glaucoma drainage devices.3
Like most angle-based procedures, GATT requires the surgeon to be familiar with intraoperative gonioscopy and angle structures. These can be practised in a wetlab and/or intraoperatively after phacoemulsification.
Once the surgeon is comfortable with goniosurgery, the procedure itself has a moderate learning curve. Once mastered, it becomes a safe and cost-effective surgical option to lower intraocular pressure (IOP), as well reduce dependence on glaucoma-lowering medications.
GATT carries several advantages:
- It is minimally invasive – performed through two corneal paracentesis – and does not involve leaving a device inside the eye.
- It addresses the juxtacanalicular outflow pathway, known to have the highest resistance to aqueous outflow, thus restoring flow through the eye’s natural drainage system, rather than creating an alternative pathway into the subconjunctival space.
- It does not violate the conjunctiva; hence, it does not compromise the results of any future bleb-based glaucoma surgeries. It also avoids the risks associated with bleb-based procedures, e.g., hypotony, infection and dysthesia.
- The 360° incision directs flow into more collector channels, especially through the inferonasal quadrant, which is known to have a higher distribution of collector channels.4
- It is a low-cost procedure, as it can be performed using a prolene suture.
YASMINE M. EL SAYED, MD, MRCSED
E: [email protected]
Dr El Sayed is a glaucoma and cataract consultant professor of ophthalmology at Cairo University, Egypt. She has no financial disclosures.
1. Grover DS, Godfrey DG, Smith O, Feuer WJ, Montes de Oca I, Fellman RL. Gonioscopy-assisted transluminal trabeculotomy, ab interno trabeculotomy: technique report and preliminary results. Ophthalmology. 2014;121(4):855- 861.
2. Grover DS, Smith O, Fellman RL, Godfrey DG, Gupta A, Montes de Oca I, Feuer WJ. Gonioscopy-assisted transluminal trabeculotomy: an ab interno circumferential trabeculotomy: 24 months follow-up. J Glaucoma. 2018;27(5):393-401.
3. Grover DS, Godfrey DG, Smith O, Shi W, Feuer WJ, Fellman RL. outcomes of gonioscopy-assisted transluminal trabeculotomy (GATT) in eyes with prior incisional glaucoma surgery. J Glaucoma. 2017;26(1):41-45.
4. Elhusseiny AM, El Sayed YM, El Sheikh RH, Gawdat GI, Elhilali HM. Circumferential schlemm’s canal surgery in adult and pediatric glaucoma. Curr Eye Res. 2019;44(12):1281-1290
5. Guo CY, Qi XH, Qi JM. Systematic review and meta-analysis of treating open angle glaucoma with gonioscopy-assisted transluminal trabeculotomy. Int J Ophthalmol. 2020;13(2):317-324