Five-year results of illuminated microcatheter-assisted gonioscopy-assisted transluminal trabeculotomy in the Indian population – A retrospective study

Abstract

Purpose:

To assess 5-year outcomes regarding the efficacy and safety of gonioscopy–assisted transluminal trabeculotomy (GATT) using an illuminated microcatheter in glaucoma patients in India.

Methods:

This retrospective study analyzes clinical records of 110 primary and secondary glaucoma patients treated with either GATT or GATT combined with cataract surgery (GATT+CS) from August 1, 2014 to July 31, 2019 at a single clinical center by one surgeon. The main postoperative outcomes assessed included changes in intraocular pressure (IOP), the use of anti-glaucoma medications (AGMs), the occurrence of complications, and surgical success over a 5-year follow-up period. Absolute success was characterized by an intraocular pressure of ≤18 mmHg, without AGM, and a 30% reduction from baseline.

Results:

The average IOP and AGM reduced from 26.46 ± 9.97 mmHg and 2.60 ± 1.27 preoperatively to 13.02 ± 2.01 mmHg and 1.16 ± 1.28 five years after the procedure. The visual acuity improved from 0.89 ± 0.58 to 0.34 ± 0.6 two months after surgery. The absolute and qualified success rates were 50% and 96.55%, respectively, at the 5-year follow-up. Kaplan–Meier analysis showed a 5-year survival rate of 89.46% (95% CI: 82.82–96.12%). A comparison between POAG and PACG showed 5-year survival probabilities of 73.8% and 94.4%, respectively. Although the number of secondary glaucoma eyes was small, they were retained to represent real-world clinical diversity; results are interpreted with caution. Complications observed included transient hyphema (94.5%), vitreous hemorrhage (1.8%), peripheral Descemet’s detachment (2.7%), and blood behind the intraocular lens (1.8%). All complications except hyphema took place during the early phase of the study (2014–2015), and none resulted in vision loss at the 3-month follow-up.

Conclusions:

Both GATT and GATT+CS are safe and effective surgical treatments for different types of glaucoma. These findings provide long-term evidence on the efficacy and safety of illuminated microcatheter-assisted GATT in Indian eyes.

Glaucoma remains a major public health concern, impacting around 11.2 million people in India as of 2010.[1] Despite its complications, trabeculectomy remains the preferred surgical option for treating glaucoma in India.[2,3] Gonioscopy-assisted transluminal trabeculotomy (GATT), described by Grover et al.[4] in January 2014, utilizes an illuminated microcatheter and has demonstrated promising results in patient outcomes. Other trabeculotomy techniques include using a 5-0 Prolene suture,[5] the bent ab-interno needle goniotomy,[6] the TANITO microhook,[7] and the TRAB 360 device.[8] Although extensive long-term data demonstrate the safety and effectiveness of GATT in Western populations, similar long-term data are lacking for the Indian population.[9] This study aimed to evaluate whether GATT surgery offers a sustained, clinically meaningful reduction in IOP and reduces the use of AGM in patients with glaucoma. An additional goal was to document any intraoperative or postoperative complications associated with the procedure and to report any novel findings.

Methods

Institutional Ethics Committee approval (EC/NEW/INST/2023/PB/0275) was obtained on October 21, 2024, prior to commencing the study. The study complied with the principles set out in the Declaration of Helsinki. The requirement for informed consent was waived. This retrospective study analyzed the clinical records of patients with primary or secondary glaucoma who underwent the GATT procedure for glaucoma at a single clinic in North India, performed by one surgeon between August 1, 2014 and July 31, 2019. Patients were excluded if their GATT surgery was not completed or if they had less than 1 year of follow-up. Preoperative data collected from clinical records included age, gender, comorbidities such as hypertension and diabetes, visual acuity, intraocular pressure (IOP) measured by Goldmann applanation tonometry, use of antiglaucoma medications, Humphrey visual fields (HVF), and the type of glaucoma. The record of surgery types includes GATT alone or GATT combined with cataract extraction and IOL implantation (GATT+CS). Eyes with primary angle-closure glaucoma (PACG) that had previously undergone cataract surgery, still showing more than three quadrants of irido-trabecular synechiae on gonioscopy, and needing AGM to manage IOP, were classified as PACG pseudophakia (PACG–P). These eyes were analyzed alongside phakic PACG eyes during the statistical process, as part of the PACG group (PACG + PACG-P). Clinical records were reviewed for details of the procedure, including the extent of trabeculotomy, any drugs used intraoperatively, and any documented complications. Postoperative data on visual acuity, use of AGM, fundus examination, gonioscopy findings, and any complications were collected from clinical records during follow-up visits at 1, 3, 6, 12, 24, 36, and 60 months. Where available, preoperative and postoperative optical coherence tomography (OCT) images of the angle were reviewed. Pre- and postoperative scans were available for 28 eyes (19 PACG, 9 POAG). All scans were performed nasally using the Optovue RTVue device (Optovue Inc., Fremont, CA, USA) with the angle scan protocol (AS-OCT single line - angle 3 mm scan). The protocol was consistent across patients. Quantitative iridotrabecular contact (ITC) analysis was not consistently available as OCT scans were limited to the nasal quadrant and not performed before and after surgery in all eyes.

All phakic PACG eyes underwent GATT+CS. Standalone GATT was performed only in POAG eyes (both phakic and pseudophakic) or in pseudophakic PACG eyes. In all cases involving GATT+CE, phacoemulsification with IOL implantation was performed prior to GATT.

Patients provided informed consent for the surgery after being informed about all related risks and benefits. After sterile eye draping, 3 ml of sub-Tenon xylocaine was injected into the inferior temporal quadrant of the operative eye. A 2.8 mm limbal incision was performed using a keratome (Alcon Laboratories, Fort Worth, TX, USA) on the temporal side in all right eyes and on the superonasal side in all left eyes, with the surgeon seated superiorly. In combined cases, before performing the trabeculotomy, the pupil was constricted using 0.1 ml of intracameral 0.5% Pilocarpine nitrate. Three 1.2 mm corneal stab incisions were made using a 15-degree side port knife (Appasamy Associates, Chennai, India) at the superior, inferior, and temporal locations, respectively. The anterior chamber was filled with a cohesive viscoelastic substance (Healon GV^TM, 1.4% sodium hyaluronate, Johnson and Johnson Vision). The patient’s head would be tilted 30 degrees away from the surgeon, and the microscope would be tilted 30 degrees toward the surgeon. A Swan Jacob gonio lens (Ocular Instruments Inc., Bellevue, WA, USA) was used to visualize the anterior chamber angle. An illuminated microcatheter was inserted into the anterior chamber via either the inferior or superior side port. Between 2014 and 2018, the Glaucolight^TM illuminated microcatheter (DORC International, Zuidland, Netherlands) was used. From 2018 onward, due to the unavailability of Glaucolight^TM, the iTrack^TM 250 microcatheter (Ellex iScience Inc., Fremont, CA, USA) was used. The approximate costs were INR 15,000 for Glaucolight and INR 45,000 for itrack 250. A 26- or 30-gauge needle inserted through the temporal side port was used to perform a one to two clock hour goniotomy at the anterior edge of the pigmented trabecular meshwork. A 23-G micro forceps (Micro Surgical Technology, MST Inc., Redmond, WA, USA) was inserted through the temporal side port and used to grasp the tip of the microcatheter, guiding it into Schlemm’s canal via the created goniotomy. The microcatheter’s illuminated tip indicated its progress as it was steadily advanced within the canal using micro forceps. After the microcatheter tip completed a full 360 degrees around Schlemm’s canal and re-emerged at the goniotomy site, it was grasped with the micro forceps. The gonio lens was then removed, and while holding the illuminated tip, the outside part of the microcatheter was pulled with another forceps. This manoeuver allowed the catheter to cut through the trabecular meshwork, resulting in a complete 360-degree trabeculotomy [Video 1]. The viscoelastic was removed from the anterior chamber through irrigation and aspiration. The side ports were hydrated, and the eye was patched.

Minor variations from Grover et al.’s[4] original technique included performing GATT after cataract surgery, using a needle instead of a microsurgical blade to create the goniotomy, and ensuring no viscoelastic remained in the eye at the end of surgery.

In the PACG group, a limited anterior synechialysis was performed to visualize the trabecular meshwork before initiating goniotomy. Synechialysis was performed using the same 26- or 30-G needle tip, applying a gentle posterior sweeping motion to avoid damaging the iris fibers or trabecular meshwork. Postoperatively, all patients were prescribed gatifloxacin (0.3%) eye drops four times daily for 5 days. Difluprednate (0.05%) eye drops were prescribed four times daily, with the frequency gradually reducing weekly over 4 weeks for GATT alone, or over 6 weeks for GATT+CS. Difluprednate was selected for both GATT and GATT+CS cases because of its strong anti-inflammatory effect, which may help prevent early development of peripheral anterior synechiae.[10,11,12] Pilocarpine 2% eye drops were prescribed three times daily for the first 2 weeks to prevent peripheral anterior synechiae. An IOP spike was defined as a measurement exceeding 30 mmHg or a rise of more than 10 mmHg from baseline within 1 to 4 weeks. In case of an early IOP spike (within the first week after surgery), oral acetazolamide 250 mg twice daily was started for 5 days. For the delayed IOP spike (after the first week),[13] difluprednate was replaced with 0.2% loteprednol etabonate, and topical AGM was started. The preferred AGM was a fixed combination of Timolol and Pilocarpine, administered twice daily.

All statistical analyses were performed using IBM SPSS v28 and Python. Continuous variables such as IOP, AGM use, and visual acuity were reported as means with standard deviations (SDs). Their normality was assessed using the Shapiro–Wilk test. For normally distributed data, paired t-tests were used to compare preoperative and postoperative values. Independent t-tests were used for intragroup comparisons. Categorical variables, like postoperative complications, were presented as counts and percentages. Surgical success over time was assessed using the Kaplan–Meier analysis, with subgroup differences analyzed using the log-rank test. Absolute success was characterized by an intraocular pressure of ≤18 mmHg, without AGM, and a 30% reduction from baseline. Qualified success was defined as an IOP ≤18 mmHg, with the same or fewer medications as at baseline, accompanied by a 30% reduction in IOP. Failure was defined as an IOP >18 mmHg on two consecutive visits, a reduction in IOP of less than 30% from baseline, an IOP ≤ 5 mmHg, or requiring additional glaucoma surgery. The IOP thresholds used to define surgical success in this study align with previous GATT literature.[13] A more stringent 30% IOP reduction threshold was adopted due to the advanced disease status in many patients and the variety of glaucoma types and surgical combinations in the study population.[14]

Results

Out of 128 records screened, 18 were excluded (incomplete records in five and less than 1 year follow-up in 13). A total of 110 eyes (one eye of each patient) were included. Table 1 shows the baseline characteristics of the study population. The case numbers at annual follow-ups were 110 after 1 year, 81 after 2 years, 67 after 3 years, 53 after 4 years, and 58 after 5 years. No statistically significant difference was observed in preoperative IOP and AGM between the GATT and GATT+CS groups (P > 0.05). Similarly, there was no significant difference (P > 0.05) in baseline IOP and AGM values between the PACG and POAG groups. Table 2 shows the annual postoperative IOP and AGM data for the study group, including the PACG and POAG groups. The mean reduction from baseline at the 5-year follow-up was 41.42% for IOP and 56.34% for antiglaucoma medication use, both with P < 0.0001. The absolute success rates at 1, 2, 3, 4, and 5 years were 75.0%, 71.6%, 53.7%, 44.2%, and 50.0%, respectively. The qualified success rates at the same time intervals were 95.3%, 97.5%, 94.0%, 96.1%, and 96.5%.

Table 1.

Baseline characteristics of patients in the study population, n=110

Characteristics	Subgroups	Total n=110	GATT group n=32	GATT + CS group n=78
Age (years), mean±SD		60.11±14.18	55.47±19.80	62.03±10.08, P=0.565*
Sex, n (%)	Male	59 (53.63%)	25 (78.12%)	34 (43.58%), P=0.006†
	Female	51 (46.36%)	7 (21.8%)	44 (56.41%), P=0.006†
Diagnosis, n	POAG (%)	26, (23.6%)	11, (34.4%)	15, (19.2%)
	PACG group (PACG + PACG-P) (%)	65, (59.1%)	11, (34.4%)	54, (69.2%)
	Pseudoexfoliation glaucoma (%)	2, (1.8%)	0, (0%)	2, (2.5%)
	Uveitic glaucoma (%)	5, (4.5%)	1, (3.1%)	4, (5.1%)
	Steroid-induced glaucoma (%)	3, (2.7%)	1, (3.1%)	2, (2.5%)
	Post PKP glaucoma (%)	1, (0.9%)	1, (3.1%)	0, (0%)
	JOAG (%)	7, (6.3%)	7, (21.8%)	0, (0%)
	Angle recession glaucoma (%)	1, (0.9%)	0, (0%)	1, (1.2%)
Previous glaucoma surgery, n	Trabeculectomy (%)	10, (11%)	3, (9.3%)	7, (8.9%)
	Canaloplasty (%)	1, (0.9%)	1, (3.1%)	0, (0%)
Preoperative IOP (mmHG), mean±SD		26.46±9.97	27.97±11.32	26.06±9.52, P=0.41*
Preoperative AGM, mean±SD		2.60±1.27	3.16±1.25	2.39±1.22, P=0.005*
Cup disc ratio, mean±SD,		0.83±0.15	0.9±0.12	0.80±0.15, P=0.00015*
Mean BCVA logMAR, mean±SD		0.91±0.58	0.94±0.74	0.90±0.5, P=0.014*

*Welch’s t-tests. ^†Chi-square test. ^††AGM: Antiglaucoma medication; BCVA: Best-corrected visual acuity; CS: Cataract surgery; GATT: Gonioscopy-assisted transluminal trabeculotomy; IOP: Intraocular pressure; JOAG: Juvenile open-angle glaucoma; %: Percentage; POAG: Primary open-angle glaucoma; PACG: Primary angle-closure glaucoma; PACG-P: Primary angle closure glaucoma- pseudophakia; PKP: Penetrating keratoplasty; SD: Standard deviation

Table 2.

Annual postoperative intraocular pressure and antiglaucoma medication data for the study population, including both the primary angle closure and primary open-angle glaucoma groups

	Total (n)	PACG (PACG + PACG-P) (n)	POAG (n)	P*
Preop IOP, mmHg n=65 PACG and 26 POAG	26.46±9.97, 110	26.5±9.46, (65)	23.38±7.46, (26)	0.078
Preop AGM	2.60±1.27	2.57±1.25	2.11±1.14	0.086
1-year IOP, mmHg, reduction percent	13.98±3.77, 40.68%	13.16±2.35, 50.34%	16.62±5.96, 29.0%	0.007
1-year AGM, reduction percent	0.35±0.80, 86,52%	0.31±0.77, 87.55%	0.38±0.30, 81.99%	0.7409
2-year IOP, mmHg, reduction percent	13.36±2.30, 41.81%	13.23±2.23, 49.85%	14.19±2.67, 39.30%	0.1942
2-year AGM, reduction percent	0.53±0.88, 82.57%	0.34±0.76, 86.78%	0.95±0.97, 54.97%	0.0172
3-year IOP, mmHg, reduction percent	14.16±3.95, 39.84%	13.66±2.23, 48.53%	14.46±2.61, 38.15%	0.2929
3-year AGM, reduction percent	1.04±1.29, 64.47%	0.94±1.30, 63.42%	1.2±1.08, 43.12%	0.2672
4-year IOP, mmHg, reduction percent	13.30±2.38, 44.12%	13.00±2.31, 50.94%	14.9±2.56, 36.27%	0.0570
4-year AGM, reduction percent	1.17±1.20, 60.03%	1.04±1.26, 59.92%	1.70±0.95, 19.43%	0.0976
5-year IOP, mmHg, reduction percent	13.01±2.01, 41.42%	12.8±1.78, 51.7%	13.92±2.87, 40.55%	0.2265
5-year AGM, reduction percent	1.16±1.28, 56.34%	1.08±1.38, 57.97%	1.67±1.07, 20.85%	0.1469

*Welch’s t-test. ^†AGM: Antiglaucoma medication; IOP: Intraocular pressure; PACG: Primary angle closure glaucoma; PACG-P: Primary angle closure glaucoma–pseudophakia; POAG: Primary open angle glaucoma; SD: Standard deviation

IOP and AGM reduction was significant over 5 years across multiple groups: PACG (51.7% and 58.0%), POAG (40.5% and 20.9%), JOAG (46.3% and 79.0%), pseudoexfoliation glaucoma (53.9%and 100.0%), steroid-induced glaucoma (30.2% and 75.0%), post-penetrating keratoplasty glaucoma (51.7% and 66.6%), and uveitic glaucoma (53.9% and 33.3%) (P < 0.0001). There was only one eye with angle recession glaucoma, and this eye failed in the third year and required trabeculectomy.

Table 1 also compares IOP and AGM outcomes between the POAG and PACG groups. Both the PACG and POAG groups showed a sustained reduction in IOP and AGM use over time. The PACG group consistently used fewer antiglaucoma medications, indicating a reduced medication burden for these eyes after surgery. At 5 years, absolute success was achieved in 57.1% of PACG eyes (n = 35) and 25% for the POAG eyes (n = 10).

Comparison of the IOP and AGM burden between the GATT and combined groups showed that preoperatively, the mean IOP was similar (GATT: 27.97 ± 11.32 mmHg vs. Combined: 26.06 ± 9.52 mmHg; P = 0.41), while mean AGM use was higher in the GATT group (3.16 ± 1.25 vs. 2.39 ± 1.22; P = 0.005). Postoperatively, there was no significant difference in mean IOP between the groups, except at Year 4, when the GATT group had lower IOP (12.50 ± 2.16 mmHg vs 13.81 ± 2.44 mmHg; P = 0.049). At 5 years, the IOP showed a reduction of 47.85% in the GATT group and by 37.20% in the combined group (P < 0.0001). At the same time point, medication use was reduced by 39.06% in the GATT group and by 68.38% in the combined group (P < 0.0001). AGM usage stayed consistently higher in the GATT group across all follow-up visits, indicating a larger medication burden in that group despite similar IOP control. Table 3 compares the IOP and AGM outcomes between the GATT and combined procedures in both POAG and PACG groups. The PACG group consistently exhibited a greater percentage reduction in both IOP and AGM use across all treatment types and time points. The differences in IOP were statistically significant at years 1 and 4 (P < 0.05), and the difference in AGM use reached statistical significance at year 4 (P < 0.0001).

Table 3.

Reduction in intraocular pressure and antiglaucoma medication based on diagnosis and type of surgery

	GATT-POAG	Combined -POAG	GATT-PACG (P)	Combined -PACG group (P)
Total, n	11	15	11	54
Mean age±SD, year	58.45±14.49	63.93±9.95	70.09±9.78 (0.0409)	62.05±10.88 (0.7693)
Preop mean IOP±SD, mmHG	22.63±7.78	23.93±7.44	29.18±9.78 (0.0988)	25.94±9.39 (0.1303)
Preop mean AGM±SD	2.45±1.44	1.87±0.83	3.36±1.02 (0.1053)	2.40±1.24 (0.1072)
1-year IOP reduction %,	20.88%	35%	52.03% (0.1589)	51.29% (0.0093)
1-year AGM reduction %,	77.78%	82.61%	75% (0.584)	90% (0.6936)
2-year IOP reduction %,	39.32%	37.68%	55.23% (0.5619)	45.44% (0.3761)
2-year AGM reduction %,	47.83%	57.89%	89.47% (0.0438)	85.54% (0.1829)
3-year IOP, reduction %,	28.16%	30.91%	51.81% (0.3481)	44.89% (0.3748)
3-year AGM reduction %,	30.43%	45.45%	36.36% (0.7522)	73.33% (0.4015)
4-year IOP reduction %,	42.4%	31.25%	68.42% (0.025)	46.64% (0.6634)
4-year AGM reduction %,	31.25%	25%	44.44% (0.8264)	72.06% (0)
5-year IOP reduction %,	43.01%	29.07%	63.3% (0.1666)	45.24% (0.3652)
5-year AGM reduction %,	33.33%	33.33%	30.43% (0.4802)	66.67% (0.2572)

*Welch’s t-tests. ^†AGM: Antiglaucoma medication; IOP: Intraocular pressure; GATT: Gonioscopy-assisted transluminal trabeculotomy; CS: Cataract surgery; POAG: Primary open-angle glaucoma; PACG: Primary angle-closure glaucoma

Kaplan–Meier survival analysis showed an overall cumulative survival probability of 89.46% (95% CI: 82.82–96.12) at 5 years. Subgroup analysis comparing PACG and POAG groups showed 5-year cumulative survival rates of 96.42% (95% CI: 86.0-100) and 73.84% (95% CI: 53.4-94.2), respectively. The 5-year cumulative survival rates were 88.7% (95% CI: 76.5-100) for GATT and 90.4% (95% CI: 83.1-97.7) for combined groups. The log-rank test showed no significant difference (P = 0.928) [Fig. 1].

Figure 1.

(a) Kaplan–Meier curve showing the cumulative probability of surgical success. The shaded area represents 95% confidence intervals. Censoring was accounted for. (b) The Kaplan–Meier curve shows that POAG has a steeper decline in survival after 3 years, while PACG maintains better long-term outcomes. (c) Kaplan–Meier curve comparing GATT and GATT+CS subgroups, showing no significant difference

No statistically significant difference in efficacy was found between eyes operated using either the Glaucolight or the iTrack microcatheter (P > 0.05).

The mean logMAR visual acuity significantly improved from 0.89 ± 0.58 before surgery to 0.34 ± 0.6 at 2 months postsurgery (P < 0.0001). Sixty-six eyes gained more than two lines of vision, while 44 eyes experienced no change. Postoperative visual acuity was significantly better in the GATT + CS group compared to the GATT group (P = 0.014).

Visual field data showed a baseline mean deviation (MD) of -20.83 ± 8.78 dB, which remained relatively unchanged at -21.12 ± 8.92 dB after 5 years. The average annual MD change was +0.29 ± 1.5 dB. No significant progression in visual field loss was observed during this period (P > 0.05).

OCT images of the nasal angle in operated eyes frequently displayed a posterior flap of the cut trabecular meshwork. Smith[15] initially mentioned this, and it was later referred to as the trabecular shelf by Grover et al.,[4] based on gonioscopic findings. Some OCT images showed a trabecular flap closing the trabeculotomy, while others showed the flap being pulled away from the trabeculotomy due to its strong attachment to the peripheral iris. The closed flaps were observed in five POAG cases, while the retracted trabecular shelf was seen only in 14 PACG cases [Fig. 2]. However, limited numbers and sectoral scans (nasal) preclude any firm conclusions.

Figure 2.

(a) Anterior segment OCT in a PACG eye post-GATT shows the trabecular meshwork flap retracted posteriorly and adherent to the peripheral iris (indicated by the arrows). (b) Anterior segment OCT in a POAG eye post-GATT shows the trabecular meshwork flap collapsing onto the trabeculotomy site (blue arrows indicate both the trabecular meshwork flap and the trabeculotomy site)

The most common complication was hyphema, occurring in 104/110 eyes (94.5%). Early hyphema was seen in 93/104 (89.4%) eyes and late hyphema in the remaining 11/104 (10.6%) eyes. Two patients on oral anticoagulants required an anterior chamber wash (1.8%) due to persistent hyphema despite having discontinued the medication 5 days before surgery. In two eyes (1.8%), blood was trapped between the intraocular lens and posterior capsule, requiring a YAG laser capsulotomy after 2 weeks. IOP spikes were observed in 7/110 cases (6.36%), including one case with JOAG, four cases with PACG, and two cases with POAG, following the use of difluprednate. Limited peripheral Descemet’s membrane detachment was observed in three eyes (2.7%). Injection of a large air bubble into the anterior chamber resolved the detachment within a week. Two cases (1.8%) of vitreous hemorrhage resolved spontaneously within 2 months without intervention. One was pseudophakic with an anterior chamber iris claw lens, which allowed blood in the anterior chamber to access the vitreous. The other was on oral anticoagulant medication, which had been discontinued 5 days before surgery. Repeat glaucoma surgery (trabeculectomy) due to elevated IOP was performed in five (4.5%) cases. No cases of hypotony, choroidal detachment, shallow anterior chamber, or retinal detachment were reported.

Discussion

Minimally invasive glaucoma surgery (MIGS) is increasingly being adopted in India for treating both pediatric and adult patients with glaucoma.[16,17,18,19] For adult glaucoma, a 5-0 Prolene suture is more frequently used than the illuminated microcatheter, likely due to cost considerations.[20,21,22] GATT surgery provides the advantage of preserving the conjunctiva, allowing for potential future filtration surgeries if needed.[23]

This study reports 5-year real-world outcomes of GATT performed with an illuminated microcatheter in the Indian population. Importantly, it also compares surgical results. Our analysis showed overall attrition rates of 1.8%, 26.4%, 39.1%, 51.8%, and 48.2% at 1, 2, 3, 4, and 5 years, respectively.

At the 5-year follow-up, IOP and AGM use were reduced by 41.42% and 56.34%, respectively. The cumulative failure probabilities were 1.9%, 2.9%, 7.5%, 8.9%, and 11.5% at 1, 2, 3, 4, and 5 years postsurgery.

Among the other glaucoma subtypes in the study, pseudoexfoliation eyes achieved the highest sustained long-term control, with 50% absolute success at 5 years. Steroid-induced glaucoma eyes responded very well initially, although some eventually needed medication. The uveitic glaucoma and PACG groups showed decreasing success rates, likely due to disease recurrence or scarring. JOAG maintained moderate stability, around 57% [Fig. 3]. Although the number of secondary glaucoma eyes was small, they were retained to represent real-world clinical diversity; results are interpreted with caution.

Figure 3.

Absolute surgical success rates at 1, 3, and 5 years following GATT in secondary glaucoma subtypes. Bar chart showing the proportion of eyes achieving absolute success, defined as intraocular pressure ≤18 mm Hg without antiglaucoma medication, among juvenile open-angle glaucoma (JOAG), steroid-induced, uveitic, and pseudoexfoliation groups

Liu et al.[24] reported 4-year outcomes of GATT for open-angle glaucoma, with a 46% reduction in IOP and an average reduction of 1.0 antiglaucoma medications. The overall failure rate was 51.8% at 4 years, based on an IOP threshold of 21 mmHg. Hyphema was the only noted complication. In comparison, our POAG group showed a 35.18% reduction in IOP and a 0.4-unit reduction in medication over 4 years, along with a lower failure rate of 27%. The occurrence of hyphema after surgery in our study group was 94.5%. Our efficacy data match other similar studies reporting results of GATT in POAG.[25,26]

Maheshwari et al.[27] reported a hyphema incidence of 43% in their study on suture GATT in Indian eyes, which is notably lower than our results.

Sharkawi et al.,[28] in a study on GATT for PACG (including both pseudophakic and phakic patients), reported a 48% reduction in IOP, which corresponds to 42.63% in this study, and an average decrease of 0.8 in AGM (compared to 1.5 in this study). They found no significant difference in the percentage reductions of IOP and AGM between the GATT-only group and the combined GATT and phacoemulsification group, which aligns with the findings of this study. Additionally, they observed hyphema in all cases (94.5% in this study), with four patients (two in this study) requiring anterior chamber wash. The difference in hyphema incidence may be caused by increased bleeding in PACG cases due to prior existing PAS and greater vascular congestion. However, we found no statistically significant difference in hyphema occurrence between PACG and POAG.

El Sayed et al.,[29] in a randomized controlled trial on PACG eyes comparing cataract surgery alone with GATT combined with cataract surgery, reported a 52.69% reduction in IOP. The use of AGM was reduced by 2.0 medications, with a complete success rate of 75% at 1 year. They reported 69% hyphema, and one patient with intracapsular blood after surgery underwent a YAG laser capsulotomy. These results resemble the outcomes in our study. Our hyphema incidence was likely higher because we did not leave any viscoelastic fill after the surgery.

The PACG group consistently showed greater reductions in IOP and AGM use compared to the POAG group. Furthermore, the 5-year survival probability was higher for the PACG group at 94.4%, versus 73.8% in the POAG group. This, along with the OCT images, suggests that in PACG, better outcomes may be linked to the additional benefit of cataract surgery and to trabecular flap tethering to PAS [Fig. 2]. This hypothesis needs validation through further long-term studies.

Interpreting visual field stability requires caution due to attrition bias and the floor effect.[30] Therefore, the visual field findings in this study need to be verified in a future prospective study. Although many complications were observed in the study data, complications like Descemet’s detachment and vitreous hemorrhage occurred within the first 2 years of adopting the GATT technique, suggesting that a learning curve may have influenced these outcomes. The low rate of IOP spikes (6.36%) is comparable to the very low incidence reported by Grover et al.[4] (1.9%) and consistent with absence of spikes noted by Pereira et al.[31] Our protocol of complete viscoelastic removal at the end of surgery, strict monitoring, and early switch to loteprednol in responders and concomitant use of pilocarpine may explain this low rate of IOP spikes.

We acknowledge the limitations of our study, including the variety of glaucoma subtypes, the high number of cases lost to follow-up, absence of ITC data, and the retrospective design of the study. These underscore the need for a long-term prospective study to evaluate the outcomes of GATT in the Indian population.

Conclusion

Both GATT and GATT+CS demonstrated good overall success rates in a pooled cohort of primary and secondary glaucoma. The complications were temporary, and none threatened vision.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published

Data availability

The datasets generated or analysed during the current study are available from the author upon reasonable request.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.