Factors Associated With Gonioscopy-Assisted Transluminal Trabeculotomy (GATT) Complications and Failure in Children


To identify the factors associated with the complications and failure of gonioscopy-assisted transluminal trabeculotomy (GATT) in children.


Retrospective case series.


This study was conducted in an institutional setting in a pediatric population (aged <18 years) who had undergone GATT. Records were reviewed, and pre- and postoperative intraocular pressures (IOP), extent of angle treated, medications, complications, and failure were recorded. Failure was defined as IOP >21 mm Hg or <5 mm Hg, absence of at least 20% IOP reduction, performance of additional IOP-lowering surgery, or loss of light perception vision.


A total of 74 eyes of 57 patients were included (mean age, 7.1 years). Over a median follow-up period of 28.5 months, 36 eyes (48.6%) failed. IOP spikes occurred in 25 eyes (33.8%) and were a significant risk factor for failure (hazard ratio [HR] = 2.17; P = .0207). Postoperative hyphema was a significant risk factor for IOP spike (HR = 4.13, P = .003) but not for failure (HR = 0.7, P = .2977). The risk of IOP spike was lowest in eyes treated with nonsteroidal anti-inflammatory drugs (NSAIDs; HR = 0.27, P = .0016). The risk of failure increased significantly in eyes that received topical corticosteroids (compared to NSAIDs; HR = 5.72, P = .0005), in eyes with <360 incisions (HR = 4.69, P < .0001), and in younger children.


GATT is a reasonably effective procedure in childhood glaucoma. Postoperatively, the use of topical NSAIDs (without corticosteroid) may decrease the risk of failure. Eyes with IOP spikes without hyphema are at the highest risk for failure.

T rabeculotomy ab externo was introduced in the 1960s and became a standard, effective surgical procedure for the treatment of childhood glaucoma. Early publications described the cleavage of the trabecular meshwork (TM) using either a nylon filament that was passed into the Schlemm canal, externalized, and bowstringed into the anterior chamber , or using a rigid curved metal probe that was inserted into the Schlemm canal and rotated into the anterior chamber. The rigid probe technique became the standard and allowed treatment of approximately 120° at a single surgical session. In the 1990s, cannulation of the Schlemm canal with a suture was reintroduced by Lynch and Beck, and it allowed up to 360° treatment at 1 operation. Subsequently, an illuminated microcatheter was developed, which improved visualization.

Ab interno filament trabeculotomy was described by Grover et al, who named the procedure “gonioscopy-assisted transluminal trabeculotomy” (GATT). The procedure, which requires an adequate gonioscopic view of the anterior chamber, spares the conjunctiva and has both shorter operative time and faster recovery than ab externo surgery. Since the original description of GATT, which we will refer to as “traditional GATT,” additional procedures have been described that use a retractable filament to disrupt the TM. The various operations are commonly called GATT procedures, and we will adhere to this convention.

We previously reported on the outcomes of GATT in a heterogeneous population. We found that eyes that received postoperative corticosteroids were more likely to experience an intraocular pressure (IOP) spike than those that received nonsteroidal anti-inflammatory drugs (NSAIDs), and that achieving a circumferential trabeculotomy and using only NSAIDs postoperatively may increase surgical success. This study expands on our previous work to assess the risk factors for GATT failures and complications in children.



We retrospectively reviewed the medical records of patients <18 years of age who underwent any type of GATT between December 2014 and October 2020 at the Bascom Palmer Eye Institute, University of Miami Miller School of Medicine. The study protocol was approved by the University of Miami Institutional Review Board, and it abided by the Health Information Portability and Accountability Act of 1996 and the Declaration of Helsinki.

Patients were identified using financial claims data of Current Procedural Terminology (CPT) codes for “goniotomy,” “trabeculotomy,” and/or “transluminal dilation of aqueous outflow canal; without retention of device.” Records of all eyes identified were reviewed. Eyes were included for analysis if the procedure involved an ab interno incision of the trabecular meshwork followed by the cleavage of the meshwork using a filament (either a blunted suture or an illuminated microcatheter—traditional GATT) or a retractable filament device with or without viscodilation. Eyes were excluded if there was insufficient description of the surgical techniques or no documented follow-up at Bascom Palmer Eye Institute. The surgical techniques for the various GATT procedures used are described elsewhere.

Basic demographic information including age, sex, laterality, and primary diagnosis was recorded. Preoperative and postoperative visual acuity, IOP, and number of glaucoma and postoperative anti-inflammatory medications were recorded. Preoperative IOP was defined as the mean of 2 IOP measurements immediately prior to the procedure. The postoperative follow-up schedule was typically 1 day, 1 week, 3 weeks, 3 months, and 6 months, with additional visits as needed. The patients’ postoperative regimens and the decision to use topical NSAIDs or corticosteroids were at the surgeons’ discretion. We recorded the actual reported use of medications rather than intention-to-treat use. When used, NSAID dosing was typically 4 times daily for 3 weeks. Corticosteroids were typically used 4 times daily for 1 week, then tapered over the subsequent 3 weeks. Intraoperative factors, such as type of device used, total degrees of angle incised, and other simultaneous procedures were also recorded. The type of glaucoma was based on the Childhood Glaucoma Research Network classification system.

The main outcome measure was risk of failure associated with any of the preoperative, intraoperative, and/or postoperative variables. The secondary outcome measure was risk of IOP spike associated with any of the preoperative, intraoperative, or postoperative variables.

Complications were identified as follows: (1) IOP spike defined as an increase in IOP in the operated eye to higher than preoperative IOP level at any postoperative visit within the first 3 months; or (2) decrease in visual acuity (VA) in the operative eye to worse than postoperative day 1 VA before postoperative month 3. The most common cause of decreased vision was hyphema, which was defined in this study as a blood collection in the anterior chamber >1 mm.

Failure was defined in accordance to the 2008 World Glaucoma Association consensus, as (1) IOP >21 mm Hg or <5 mm Hg on 2 consecutive follow-up visits after postoperative month 3; (2) absence of at least 20% reduction from the preoperative IOP baseline on 2 consecutive follow-up visits after postoperative month 3; (3) performance of additional glaucoma (IOP-lowering) surgery; or (4) loss of light perception vision.


Continuous variables were compared using linear mixed models to account for the correlation between both eyes of a single person or the nonparametric Kruskal−Wallis or Mann−Whitney Wilcoxon 2-sample test. Kaplan−Meier survival analysis and Cox proportional hazards regression were used to assess the time-to-events (failure and spike complications). Univariate and bivariate marginal Cox models with robust sandwich covariance matrix estimates were used to account for the correlation between both eyes of a single person. All analyses were performed using SAS software version 9.4 (SAS Institute). A P value of .050 or less was considered to be statistically significant.


A total of 74 eyes of 57 patients were included in the study, with mean age of 7.1 years at surgery (range = 2 months to 17.4 years). The median follow-up time was 28.5 months, with an interquartile range of 2.8 to 75.3 months (SD = 19.4 months). Baseline preoperative characteristics are presented in Table 1 . In all, 17 patients (34 eyes [46%]) had both eyes included in the study. A total of 54 eyes had no prior intraocular surgery, 18 eyes had prior cataract removal with anterior vitrectomy, and 2 eyes had prior pars plana vitrectomy for retinal detachment repair. No patient had undergone previous glaucoma surgery.


Baseline Characteristics of Pediatric Patients Who Had Undergone Gonioscopy-Assisted Transluminal Trabeculotomy

Mean SD No. of Eyes
Age at time of surgery, y 7.1 6.3 74
Male sex, % 52.7 N/A 39
Laterality, % right eye 47.3 N/A 35
Preoperative IOP, mm Hg 31.3 9.1 74
No. of preoperative IOP-lowering medications 2.4 1.4 74
Diagnosis, %
Eyes with primary congenital glaucoma 28.4 N/A 21
Eyes with juvenile open-angle glaucoma 23.0 N/A 17
Eyes with glaucoma following cataract surgery 17.6 N/A 13
Eyes with other diagnoses 31.1 a 23 a
Race, %
Hispanic 40.5 N/A 30
Black 37.8 N/A 28
White 16.2 N/A 12
Asian 2.7 N/A 2
Middle Eastern 2.7 N/A 2
Lens Status, %
Phakic 74.3 N/A 55
Pseudophakic 6.8 N/A 5
Aphakic 18.9 N/A 14

IOP = intraocular pressure; N/A = not available.

a Glaucoma associated with nonacquired systemic disease or syndrome (4 eyes), glaucoma associated with nonacquired ocular anomalies (7 eyes), and glaucoma associated with acquired conditions (12 eyes).

A 360° trabeculotomy was performed in 54 eyes (73%). For all eyes, a mean of 316.9° (SD = 76.5°) of TM was incised. Between different diagnostic categories, glaucoma associated with nonacquired ocular anomalies had the highest proportion of 360° trabeculotomy (100.0%), followed by glaucoma associated with acquired conditions (91.7%), glaucoma following cataract surgery (84.6%), juvenile open angle glaucoma (76.5%), primary congenital glaucoma (52.4%), and glaucoma associated with nonacquired systemic disease/syndrome (25.0%, exact χ 2 P = .0092). In 4 eyes, trabeculotomy was combined with another procedure: cataract removal (n = 1), goniosynechialysis (n = 1), and pupilloplasty (n = 2). A total of 24 eyes (32.4%) underwent GATT with use of a retractable filament device, 17 with the TRAB360 device and 7 with the OMNI device (Sight Sciences). The remaining 50 eyes (67.6%) underwent traditional GATT with either an illuminated microcatheter (n = 44) or a blunted polypropylene suture (n = 6) manipulated with intraocular forceps.

The postoperative outcomes are reported in Table 2 . Clinically significant postoperative complications included hyphema in 36 eyes (48.6%), vitreous hemorrhage in 1 aphakic eye (1.4%), and IOP spike in 25 eyes (33.8%). Intraoperative and early postoperative hyphemas lasted an average of 11.5 days (SD = 21.6 days; range = 0-107 days). All resolved spontaneously, most within the first month after surgery. Developing a hyphema was associated with an increased risk of IOP spike (hazard ratio [HR] = 4.13; P = .003) ( Table 3 , Figure 1 ), but not of treatment failure (HR = 0.7, P = .2977) ( Table 4 ). The vitreous hemorrhage, which occurred in an aphakic patient, was noted at the 1-month postoperative visit and had cleared spontaneously at the next follow-up visit 7 months after the surgery.


Surgical Outcomes of Children Who Underwent Gonioscopy-Assisted Transluminal Trabeculotomy

Mean and Percentage SD No. of Eyes
Before surgery Mean
Preoperative IOP, mm Hg 31.3 9.1 74
No. of preoperative IOP-lowering medications 2.4 1.4 74
After surgery Mean
Mean IOP at postoperative month 3, mm Hg 17.4 7.2 62
No. of IOP-lowering medications at postoperative month 3 1.2 1.4 63
Final mean postoperative IOP, mm Hg 15.5 4.6 74
Final mean postoperative no. of IOP-lowering medications 1.1 1.3 74
Postoperative regimen, complications, and failures Percentage
Used postoperative NSAIDs, % 36.5 N/A 27
Used postoperative corticosteroids, % 54.1 N/A 40
Used neither NSAIDs nor corticosteroids 9.5 N/A 7
Hyphema, % 49.3 N/A 36
IOP spike, % a 33.8 N/A 25
Treatment failure, % 48.6 b N/A 36 b

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Sep 11, 2022 | Posted by in OPHTHALMOLOGY | Comments Off on Factors Associated With Gonioscopy-Assisted Transluminal Trabeculotomy (GATT) Complications and Failure in Children
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