Outcomes of bent ab interno needle goniectomy with phacoemulsification in moderate to severe primary open angle glaucoma

Abstract

Purpose:

To assess the safety and efficacy of bent ab interno needle goniectomy (BANG) in moderate to severe primary open angle glaucoma (POAG) eyes undergoing phacoemulsification (phaco).

Design:

Single-arm, prospective, interventional study.

Methods:

POAG patients with medically uncontrolled intraocular pressure (IOP), >15 mmHg for moderate and >12 mmHg for severe POAG, with visually significant cataract were recruited. All patients underwent BANG using a 26-gauge needle to excise 30° of the trabecular meshwork, along with phaco. Primary outcome was IOP. Secondary outcomes were success rate, percentage reduction in IOP/antiglaucoma medications (AGMs), and intraoperative complications. Success at 12 months was defined as: criterion A: IOP <15 mmHg for moderate glaucoma or <12 mmHg for severe glaucoma with or without AGMs OR criterion B: reduction in number of AGMs by >1.

Results:

Thirty-two eyes of 32 patients underwent BANG + phaco. Mean age of the participants was 62.7 ± 8.4 years and there were 25 males and seven females. At 12 months, a significant decrease was noted in both IOP (from 17.6 ± 3.6 to 12 ± 1.6 mmHg, 31.8%; P < 0.001) and AGMs (from 3.7 ± 0.9 to 2.8 ± 0.8, 24.3%; P < 0.001). Twenty percent or more reduction in IOP was achieved in 62.5% (20/32) of eyes. Overall success (meeting either of the criteria A or B) at 12 months was achieved in 87.5% eyes. Mild postoperative hyphema was noted in 10 (31.2%) eyes, and two eyes (6.2%) required additional filtration surgery at 7 months.

Conclusion:

A 30-degree BANG with phaco in patients of POAG appears to be a safe, effective and affordable MIGS for developing countries.

Primary open angle glaucoma (POAG) is characterized by progressive, irreversible optic neuropathy and visual field loss, largely due to rise in intraocular pressure (IOP). Increase in trabecular meshwork (TM) resistance is the prime factor which causes aqueous humor outflow obstruction and rise in IOP.[1,2] IOP remains the only modifiable risk factor for treating glaucoma through medical, laser, and surgical management. Trabeculectomy has been the gold standard glaucoma filtration surgery; however, the associated complications preclude its use as a primary treatment modality, especially in mild to moderate glaucoma.[3,4] In the recent past, a group of minimally invasive glaucoma surgeries (MIGS) have been developed to eliminate TM resistance using a safer and less-traumatic ab interno approach. They are suitable for mild to moderate open angle glaucoma or for eyes intolerant or unresponsive to conventional glaucoma management (medical or laser).[5] However, MIGS procedures are expensive with variable success rates, hence limiting their widespread use in developing countries.[6,7,8]

Bent ab interno needle goniectomy (BANG) with a 26-gauge needle is a cost-effective MIGS procedure designed to remove a strip of TM, allowing direct access of aqueous into Schlemm canal (SC).[9,10] Dada et al.[10,11] reported recruitment of previously collapsed aqueous outflow channels after BANG using aqueous angiography. Initial results of BANG were impressive as reported by Shute et al.,[9] using a 25-gauge hypodermic needle to remove 100° of TM. We undertook this pilot study to evaluate the efficacy of 1 clock hour BANG (30°) in eyes with moderate to severe POAG.

Methods

This single-arm, prospective, interventional study was conducted at a tertiary care university hospital in North India after obtaining clearance from the institutional ethics committee (ref. no. IEC-797/07.10.2022, RP-33/2022). The study was Health Insurance Portability and Accountability Act (HIPAA) compliant and adhered to the tenets of the Declaration of Helsinki.

POAG patients presenting at the glaucoma clinic of our center and meeting the inclusion criteria, that is, age >40 years, best corrected visual acuity (BCVA) of <20/40 by Snellen chart, IOP [with antiglaucoma medications (AGMs)] >15 mmHg for moderate glaucoma and >12 mmHg for severe glaucoma (as per the Hodapp–Parrish–Anderson classification),[12] visually significant age-related cataract, and willing to give written informed consent, were recruited between October 2022 and December 2022. Any patient unable to perform perimetry or any other retinal or optic nerve pathology causing visual field defects, patient with history of any ocular surgery in the last 12 months, history of glaucoma filtration surgery, laser treatment or angle-based surgery in the past, any anterior segment pathology precluding accurate IOP measurement, and patients unwilling to follow-up were excluded.

Baseline demographic data and details of ophthalmic evaluation were recorded for all recruited patients. Preoperative evaluation included BCVA measured using Snellen chart and converted into logarithm of minimum angle of resolution for analysis, IOP by Goldmann applanation tonometer, gonioscopy with Goldmann 2 mirror lens, detailed slit-lamp biomicroscopy, grading of the cataract as per Simple Pre-Operative Nuclear Classification Score classification and stereoscopic optic nerve head evaluation with 90 D lens, optical biometry (including pachymetry) using Lenstar (LS 900^®; Haag-Streit AG, Koeniz, Switzerland), and automated perimetry.[13] Perimetry was done on Humphrey Field analyzer (Carl Zeiss Meditec, Dublin, CA, USA) using 24-2 SITA fast algorithms. It was considered reliable when false positives and false negatives were <33% and fixation losses were <20%. All IOP measurements were taken on the same tonometer between 2 and 4 pm to avoid the effect of measurement errors and diurnal variability. All AGMs were continued preoperatively.

A single surgeon (TD) performed all surgeries. Under topical anesthesia, the eye was cleaned and draped in an aseptic manner. With the surgeon sitting on the temporal aspect, one side-port entry (1 mm) and a 2.2-mm (temporal) keratome entry were made. The anterior chamber was filled with a visco-cohesive agent. Thirty degrees was marked at the nasal limbus with a toric marker at the desired location. Microscope (toward the surgeon) and the patient’s head (away from the surgeon) were tilted for better visualization of the nasal angle. A disposable 26-gauge hypodermic needle was bent to 90° at the tip with bevel up and attached to Healon GV Pro (1.8% Sodium hyaluronate(HA)) (Johnson-Johnson Surgical Vision, Inc, Santa Ana, CA, USA) syringe. This bent 26-gauge needle was used to excise nasal 30° of TM under visualization using Swan Jacob gonioprism (University of Oregon, Portland, OR, USA) before performing capsulorrhexis for cataract surgery. Following goniectomy, the microscope and patient’s head were rotated to the primary position and standard phacoemulsification (phaco) steps were carried out to complete the surgical procedure.

Postoperatively, the patients were prescribed topical antibiotic moxifloxacin 0.5% four times daily for 3 weeks and steroid prednisolone acetate 1% six times a day, gradually tapered over 4 weeks. Prostaglandin analogs were stopped in all patients for minimum 6 weeks; later, based on postoperative IOP, AGMs were shifted/added/modified.

Patients were followed up at day 1, 1 week, 1 month, 3 months, 6 months, and 12 months postoperatively. At each follow-up BCVA, IOP, number of AGMs, and complications if any were documented. The investigator checking IOP (AB) was masked to the intervention.

The primary outcome was IOP at 12 months postoperatively. Secondary outcomes were probability of success, percentage reduction in IOP, number of AGMs, and complications if any. Success at 12 months was defined as achieving criteria A or/and B: criterion A- IOP ≤15 mmHg for moderate glaucoma or ≤12 mmHg for severe glaucoma with AGM (qualified success) or without AGM (absolute success); criterion B: reduction in number of AGMs by ≥1.

Based on previously published data, the minimum sample size required was 10 patients with 5% level of significance, 90% power of study, and 10% attrition.[9] We took a convenient sample size of 32 patients in the study. Numerical data was entered in Microsoft Excel, and IBM Statistical Package for the Social Sciences (SPSS) Statistics version 23 (SPSS, Inc., Chicago, IL, USA) was used for analysis. Parametric numerical data were recorded as mean and standard deviation, while median and range were calculated for nonparametric data. Paired t-test and Wilcoxon signed-rank test were used to assess the difference between baseline characteristics and postoperative data. A P value < 0.05 was considered significant.

Results

Thirty-two eyes of 32 POAG patients underwent BANG [Fig. 1] followed by phaco and completed minimum 12 months of follow-up. All patients belonged to northern part of the Indian subcontinent, with a mean age of 62.7 ± 8.4 years. Out of 32 patients 25 were males (78%) and 7 were females (22%). The baseline demographic data and clinical characteristics have been presented in Table 1. Twelve out of 32 patients (37.5%) had hypertension as the predominant systemic illness, and six (18.8%) had type 2 diabetes mellitus, which was well controlled. Out of 32, 11 (34.3%) eyes had severe glaucoma and 21 (65.6%) had moderate glaucoma.

Figure 1.

(a) Preoperative anterior segment optical coherence tomography. (b) Goniectomy cleft at 6 months postoperatively. (c) Goniectomy cleft at 12 months

Table 1.

Baseline demographic and clinical data

Baseline parameters		Mean±SD
Age (years)		62.7±8.4
Preoperative IOP (mmHg)		17.6±3.6
Preoperative BCVA (logMAR)		0.5±0.4
Preoperative VCDR		0.8±0.06
Preoperative number of antiglaucoma medications		3.7±0.9
Grade of cataract (based on SPONCS)		2.6±0.6
Mean CCT (μm)		525.8±10.6
Mean deviation (dB)		-11.7±7.2

BCVA=Best corrected visual acuity, DM=Diabetes mellitus, HTN=Hypertension, IOP=Intraocular pressure, logMAR=Log of minimum angle of resolution, SD=Standard deviation, SPONCS=Simple Pre-Operative Nuclear Classification Score, CCT = Central corneal thickness, VCDR = vertical cup to disc ratio

IOP significantly decreased from 17.6 ± 3.6 mmHg at baseline to 12 ± 1.6 mmHg at 12 months (31.8% decrease; P < 0.001). More than or equal to 20% reduction in IOP was observed in 20/32 eyes (62.5%) at 12 months [Fig. 2]. A significant reduction was noted in the number of AGMs from baseline (3.7 ± 0.9 to 2.8 ± 0.8 at 12 months, 24.3% reduction; P < 0.001) [Fig. 2]. For a better control of IOP, there was a trend toward increase in number of AGMs at each follow-up. However, the reduction was statistically significant at each time point from baseline.

Figure 2.

Trend of intraocular pressure and antiglaucoma medications over 12 months

Success rate at 12 months with criterion A (achieving the target IOP ≤15 mmHg in moderate glaucoma and ≤12 mmHg in severe glaucoma) was noted to be 90.4% overall success [qualified success: 18/21 (85.7%), absolute success: 1/21 (4.8%)] in moderate glaucoma and 63.6% overall/qualified success in severe glaucoma, as none achieved absolute success among severe glaucoma patients [Fig. 3]. Kaplan–Meier survival analysis was performed based on IOP, and no significant difference was observed between the two groups (P = 0.06; log-rank test) [Fig. 4]. On the whole, overall success was achieved in 26 out of 32 eyes (81.2%) eyes [qualified success: 25/32 eyes (78.1%), absolute success: 1/32 (3.1%)]. At 7 months, two eyes with severe glaucoma underwent trabeculectomy in view of uncontrolled IOP on maximal tolerable medical therapy.

Figure 3.

Success rate for defined criteria (overall, for eyes with moderate glaucoma and severe glaucoma)

Figure 4.

Kaplan–Meir survival curve for moderate and severe glaucoma

Success at 12 months with criterion B (reduction in number of AGMs ≥1) was noted in 12/21 (57.1%) eyes with moderate glaucoma and 6/11 (54.5%) eyes with severe glaucoma.

Overall success (meeting either criterion A or B) at 12 months was achieved in 28/32 (87.5%) eyes: 20/21 (95.2%) in moderate glaucoma and 8/11 (72.7%) in severe glaucoma. Conversely, both the criteria were met in 11/21 (52.4%) eyes in moderate glaucoma and 5/11 (45.4%) eyes in severe glaucoma.

Postoperatively, mild hyphema was noted in 10 eyes (31.2%), which resolved completely by 1 week on conservative management. Two eyes (6.2%) required additional filtration surgery at 7 months to achieve target IOP. None of the eyes had any complication resulting from cataract surgery. Statistically significant change in BCVA from a preoperative value of 0.5 ± 0.4 to a postoperative value of 0.2 ± 0.2 (P < 0.001) at 12 months was noted postcataract surgery.

Discussion

MIGS were introduced in the armamentarium of glaucoma management more than a decade ago. Still, there are concerns about the safety, efficacy, complications, and cost-effectiveness of different MIGS techniques.[14] In this study, we prospectively evaluated the safety and efficacy of combined cost-effective BANG with phaco in moderate to severe POAG. While there is ample literature on MIGS devices in early to moderate cases, there is paucity of data published on severe glaucoma.

In the present study, 62.5% eyes achieved ≥20% reduction in IOP at 12 months, while Shute et al.,[9] in their pilot study, observed 73% patients achieving this target at 6 months. Seventy-three percent eyes achieved IOP ≤12 mmHg at 6 months, compared to 75% eyes (24/32) in our study at 12 months. In the study by Eslami et al.,[15] a 32.1% reduction in IOP was noted after combined phaco and needle goniotomy, which was similar to the observation in the current study (31.8%). Published results of other techniques of goniotomy combined with phaco, when compared to BANG, have shown equivocal results, if not inferior.[16,17] Parikh et al.,[16] in their retrospective study, reported 18% reduction in mean IOP over 12 months in 498 eyes that underwent Trabectome combined with phaco. Dorairaj et al.[17] reported the results of Kahook Dual Blade (KDB) + phaco in 237 eyes with 24% reduction in IOP and 56.1% eyes achieving ≥20% drop in IOP.

The cumulative success as per the IOP criteria was achieved in 81.2% eyes at 1 year in our study, which is comparable to the success rates of Trabectome (71.2%) and microhook trabeculotomy (74.2%) published in Tram Trac study, even though the IOP cutoff was higher in the latter (21 mmHg).[18] Eslami et al.[15] reported complete success in 46.9% and qualified success in 62.5% eyes for an IOP cutoff of <15 mmHg at 6 months in eyes undergoing needle goniotomy. While in our study, for IOP ≤15 mmHg, qualified success was observed in 84.3% eyes (27/32) and absolute success in only one (3.1%) eye at 12 months.

In the present study, a 24.3% (0.9) reduction was observed in AGMs and 56.1% eyes had reduction of ≥1 AGM at 12 months. Eslami et al. reported a 50% (0.6) reduction in AGMs at 6 months, while Shute et al. observed a reduction of ≥1 AGM in 73% eyes at 6 months.[9,15] The relatively higher reduction in AGMs and higher percentage of patients achieving absolute success compared to the current study could be attributed to a shorter follow-up of only 6 months and majority of the population having mild to moderate disease in the aforementioned studies.[9,15] Parikh et al.,[16] also reported a 24% reduction in AGMs after combined Trabectome with phaco at 1-year follow-up. After KDB + phaco, Dorairaj et al.[17] reported reduction in AGM by ≥1 in 63.5% eyes at 12 months. Maheshwari et al.,[19] in their prospective study, observed nearly 66% reduction in AGM following ab interno microhook trabeculotomy (microLOT) combined with cataract surgery.

While majority of the reports published on ab interno goniotomy have included eyes with mild to moderate glaucoma, only a few have studied the efficacy of these procedures in severe disease.[20,21,22] With combined KDB + phaco in severe glaucoma eyes, Hirabayashi et al.[20] achieved ≤15 mmHg in 64.3%, ≤15 mmHg + AGM reduction in 45.2%, and ≤15 mmHg + complete AGM discontinuation in 31% at 6 months. The cutoff for severe glaucoma in our study was ≤12 mmHg and was achieved in 63.6%, AGM reduction was seen in 54.5%, while both targets were achieved in 45.4% of eyes at 12 months. None of the eyes with severe glaucoma achieved absolute success in this study. Salinas et al.[21] reported 6-month outcomes of KDB alone in severe/refractory glaucoma. IOP cutoff of ≤14 mmHg was achieved in 63.5% with a mean AGM reduction of 36.6%. Dang et al.,[22] in their retrospective analysis, observed a higher reduction in IOP and AGMs in eyes with severe disease, but a poor surgical success rate when compared to eyes with mild to moderate glaucoma undergoing phaco + Trabectome. The success rate of IOP ≤21 mmHg or at least 20% reduction was achieved in 74%–82% of eyes at 12 months.

The most common intraoperative or postoperative complication observed after incisional or excisional goniotomy is hyphema, which resolves spontaneously in majority of cases, rarely requiring an anterior chamber wash. In our study, hyphema was seen in 10 eyes, which resolved spontaneously over 1 week on conservative management. Authors have previously reported readhesion of TM strip post-BANG, causing failure of the procedure and subsequent rise in IOP.[23] Eslami et al.[15] reported fibrinous inflammation (3.1%) and distorted pupil (6.3%) in addition to clot hyphema (3.1%). With other methods of goniotomy (KDB, Trabectome, etc.), complications like IOP spikes, Descemet’s tear, cystoid macular edema, and epiretinal membrane have been reported. However, no such adverse events were noticed in our study.[17,20]

In our study, out of 32, only two eyes with severe glaucoma required additional glaucoma surgery (trabeculectomy) at 7 months (6.2%). Eslami et al.[15] found similar outcomes, wherein three out of 32 (9.3%) eyes required trabeculectomy (one at 3 months and two at 6 months). In eyes with severe glaucoma, Hirabayashi et al.[20] reported additional IOP-lowering procedure in 3/43 eyes (7.1%) before 5 months. Twelve months follow-up results of our study (BANG + phaco) are compared to the results of KDB + phaco and i-stent inject + phaco in Table 2.

Table 2.

Results of the current study (BANG + phaco) compared to KDB + phaco and iStent inject + phaco at 12 months

Characteristic		BANG + phaco		KDB + phacoa		iStent inject + phacob
% Reduction in IOP		31.8		26.2		9.7
% Reduction in AGMs		24.3		50		21.1
≥20% reduction in IOP (%)		62.5		57.7		50.0
≥1 AGM reduction (%)		56.2		63.5		-
Additional IOP-lowering procedure (%)		6.2		-		0

AGMs=Antiglaucoma medications, BANG=Bent ab interno needle goniectomy, IOP=Intraocular pressure, KDB=Kahook Dual Blade, phaco=phacoemulsification. ^a.Dorairaj SK, Seibold LK, Radcliffe NM, Aref AA, Jimenez-Román J, Lazcano-Gomez GS, et al. 12-Month Outcomes of Goniotomy Performed Using the Kahook Dual Blade Combined with Cataract Surgery in Eyes with Medically Treated Glaucoma. Adv Ther. 2018 Sep;35(9):1460-9. ^bShalaby WS, Lam SS, Arbabi A, Myers JS, Moster MR, Kolomeyer NN, et al. iStent versus iStent inject implantation combined with phacoemulsification in open angle glaucoma. Indian J Ophthalmol. 2021 Sep;69(9):2488-2495.

Limitations of this present study are its small sample size with a relatively short duration of follow-up and lack of a control group. Only 30° of TM was cut, and we do not know if IOP lowering would be better with a wider circumference of surgery. Some of the observed IOP lowering may be influenced by cataract extraction, but the results are considerably superior than those achieved by a cataract surgery alone.[9,15,17,20] Since it was a single-surgeon and single-center intervention trial, these results cannot be generalized. Further studies with different surgeons and with patients of varied ethnicities are recommended to establish the efficacy and safety of this technique.

A novel technique of viscodilation of SC combined with BANG using a 30-gauge needle has recently been reported, which may help to augment the safety and efficacy of BANG by reducing injury to the surrounding structures and may help to reduce the subsequent fibrotic response leading to failure of surgery.[24]

The cost of one 26-gauge disposable hypodermic needle in India is approximately 2 cents (0.02 USD), while one KDB costs around 350 USD and iStent inject costs 2000 USD. The minimal cost, ease of availability, and encouraging results make BANG a potential, implant-free MIGS technique, especially for developing countries.

This study encourages us to conduct prospective, randomized controlled trials directly comparing BANG with other techniques of cutting or stenting MIGS.

Conclusion

A 30° nasal BANG using a 26-gauge needle combined with phacoemulsification is a safe, effective, and affordable MIGS which can achieve target IOP in eyes with mild–moderate glaucoma. The results are similar to those of more expensive MIGS devices like KDB and Trabectome. This is the first prospective study to report the outcomes of BANG + phaco in severe glaucoma, and it showed encouraging results. However, majority of the patients still required AGMs, albeit fewer, to achieve a target IOP in low teens.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.