Gonioscopy-assisted transluminal trabeculotomy provides relief for patients undergoing corneal transplantation.

(Image credit: AdobeStock/Raymond Orton)

Oluwatosin U. Reviewed by Smith, MD

Glaucoma is a leading cause of vision loss worldwide, and patients undergoing corneal transplantation are considered to be at higher risk of developing glaucoma. To reduce intraocular pressure (IOP) after corneal surgery, gonioscopy-assisted transluminal trabeculotomy (GATT) may be a safe and effective alternative to conventional procedures.

The GATT procedure is performed through microscopic incisions in the cornea. An incision of approximately 1.0 mm size is made in the periphery of the cornea through which the surgery is completed. After entering the eye, the surgical procedure involves cutting the trabecular meshwork, cannulating the Schlemm’s canal 360°, and opening the roof of the Schlemm’s canal.

A retrospective analysis of patients undergoing GATT after prior corneal transplantation produced data to support the efficacy of GATT.1 Oluwatosin Smith, MD, a physician at Glaucoma Associates of Dallas, Texas, and the study’s lead author, discussed GATT as a safe and efficient intervention.

Reduction of medication burden is important for patients after corneal transplantation, such that some participants started the study on 4 or more medications.

study group demographics

The case series documented a group of 32 patients and 39 eyes, all patients with glaucoma and a history of prior corneal surgery (figure 1, The authors consider this to be the largest group with characteristics to undergo clinical review to date.1 Patient age ranged from 24 to 94 years (mean 68.0 years); 44% of participants were female and 81% were Caucasian. Prior corneal surgical procedures included penetrating keratoplasty (59.0%), Descemet stripping endothelial keratoplasty (35.9%), Descemet membrane endothelial keratoplasty (2.6%), and deep anterior lamellar keratoplasty (2.6%). In most cases, GATT was executed as a standalone process. In one instance it was performed in combination with cataract extraction/intraocular lens insertion; In the second, GATT was performed with goniosynechiasis. All GATT procedures were performed by physicians at Glaucoma Associates of Texas between January 2016 and December 2019.

In the study group, 35 patients (89.7%) had had one prior corneal surgery, whereas 4 patients (10.3%) had had multiple corneal surgeries (range, 2–7).1 Secondary open-angle glaucoma was the most common (64.1%), followed by steroid-induced glaucoma (23.1%). Specifically, patients with secondary open-angle glaucoma had no glaucoma before corneal transplantation. At the 24-month visit, 20 eyes (51.3%) had completed follow-up data.

Gait after cornea surgery

Treating elevated IOP in eyes with glaucoma after corneal transplant surgery is challenging, Smith said, because surgeons must minimize potential insult to the corneal graft tissue. After GATT, a significant reduction in IOP was observed in most patients, as well as a reduction in medication burden at all post-operative time points (Figure 2, The study authors censored patients who required reoperation to control IOP (Why<.001) From these data obtained at the 24-month visit: At 24 months, IOP decreased from baseline 30.9±11.5 to 13.9±4.7 mm Hg. Medications decreased from 4.2±1.0 medications at baseline to 0.6±1.0, and 88% of patients completing the study remained on chronic topical steroids for graft maintenance.1

Subsequently, 69% of eyes had at least 1 early complication. Postoperative complications noted at week 1 included hyphema (59%), corneal edema (18%), and vitreous prolapse (1%). At 1 month, 77% had no complications, 13% reported persistent hyphema, and 10% (4 eyes) reported corneal edema. Between 3 and 9 months, corneal edema resolved in 75% of eyes; The first eye with persistent inflammation had corneal inflammation before GATT surgery.

After undergoing GATT, 7 eyes required reoperation for uncontrolled glaucoma at a median of 8.5 months (range, 1.6-16.2). The cumulative proportion of eyes requiring further surgery to control IOP was 10.3% (95% CI, 80%–99%) at 12 months, which increased to 20.3% (95% CI, 67%) at 24 months after GATT. %-94%) done.

One month after surgery, visual acuity decreased in all eyes. Why< .05); But the authors said, "these outweighed the losses at 3 to 36 months with 2-Snellen line correction at subsequent follow-up visits." cornea, and 1 eye had a tube shunt with corneal disruption and inflammation.

Given the safety and efficacy results of the GATT procedure in patients following corneal transplantation, Smith advocated repeat surgery as a suitable option for patients who develop glaucoma after transplantation. That said, GATT is particularly prudent when applied as part of a conventional approach in the early stages of glaucoma development.

“There are patients for whom this is optimal, usually people who don’t have secondary angle closure,” Smith said. “The reason for their increased pressure may be related to prior surgery or corneal transplantation.”

Smith said physicians should pay attention to GATT, especially when the drainage device may pose a risk to the implanted tissue.

“The advantage of doing surgery without hardware in the eye is that you’re not leaving anything in the eye,” he said. “If you have a drainage implant, because it is a foreign body, there is a risk of graft failure, exposure of the implant device, and possible complications of infection.”

“For patients who have open-angle glaucoma, we need to look at the risks versus benefits of doing more traditional surgery,” Smith concluded. “When you have a choice where the risks are low and the benefits are very high, the comparison of procedures encourages you to go ahead and consider GATT as an option.”

Oluwatosin U. Smith, MD
Questions: 214-360-0000
E: tsmith@glaucomaassociates.com
Smith is an attending physician and surgeon
Founding board member of Glaucoma Associates of Texas and the Cure Glaucoma Foundation.
1. Smith OU, Butler MR, Grover DS, et al.
Twenty-four month results of hanoscopy-
Assisted transluminal trabeculotomy (GATT) in eyes with prior corneal transplant surgery. J Glaucoma, 2022;31(1):54-59. DOI: 10.1097/ijg.000000000001949

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