Peripheral Iris Cerclage in Angle Closure Glaucoma: A Retrospective Pilot Study

Abstract

Purpose

To describe a novel surgical technique using peripheral iris cerclage (PIC) and evaluate clinical and anatomical outcomes in eyes with angle-closure glaucoma (ACG).

Methods

Single-center retrospective pilot study of 8 consecutive eyes (7 patients) with ACG at high risk of recurrence undergoing peripheral iris cerclage (2010–2025), with adjunctive procedures. Primary outcomes were postoperative Shaffer angle grade and peripheral anterior synechiae (PAS). Secondary outcomes included surgical success, intraocular pressure (IOP), and glaucoma medication use. Surgical success was defined as IOP ≤18 mmHg with ≥20% reduction from baseline, without clinical hypotony (IOP <6 mmHg accompanied by ≥2-line loss of visual acuity from baseline). Eyes that underwent surgical revision, reoperation or developed no light perception vision were classified as failures. Complete success required no glaucoma medications; qualified success permitted glaucoma medications.

Results

Median Shaffer angle grading (interquartile range [IQR]) increased significantly from 0 (0–0) to 3 (3–3) (P=0.01), and PAS also significantly decreased in all eyes (P=0.03), with 6 eyes (75%) demonstrating no PAS. Postoperative imaging demonstrated relative thinning of the peripheral iris and widening of the angle. Median IOP decreased from 33.5 (31.2–43.5) mmHg to 12.0 (10–15) mmHg (p=0.01) and medication classes decreased from 4 (4–4) to 2 (1–3) (p=0.04). Two eyes (25.0%) achieved complete success, while 7 eyes (87.5%) achieved qualified success. No intraoperative complications occurred. One patient required secondary glaucoma surgery.

Conclusion

Peripheral iris cerclage was associated with sustained angle widening, favorable PAS outcomes, and substantial IOP reduction in this pilot series. This technique may serve as a useful adjunct in the surgical management of glaucoma, particularly in ACG eyes with flaccid iris tone, a high or thick iris insertion, and risk of recurrent synechiae.

Introduction

Angle-closure glaucoma (ACG) occurs when the peripheral iris obstructs the trabecular meshwork (TM), reducing aqueous outflow and causing elevated intraocular pressure (IOP), leading to a progressive glaucomatous optic neuropathy.¹ Chronic disease can lead to the formation of peripheral anterior synechiae (PAS), which may permanently close portions of the angle and reduce the efficacy of medical and laser therapies.²

Management of ACG includes laser peripheral iridotomy (LPI), lens extraction, goniosynechialysis (GSL), endocycloplasty (ECPL), and glaucoma filtration surgery.^3,4 Some have recently advocated the addition of microinvasive glaucoma surgery (MIGS) in certain cases.^5,6 These procedures aim to relieve pupillary block, rotate the iris posteriorly, deepen the anterior chamber, open the angle and/or provide alternative pathways for aqueous outflow.^7–10 In eyes with persistent IOP elevation despite angle-opening procedures or advanced disease, traditional glaucoma filtration surgery such as trabeculectomy or tube shunts may be needed. While effective at lowering IOP, these external drainage procedures do not directly address the underlying angle-closure mechanism, PAS, and are associated with serious potential early and late risks which are higher in ACG eyes.

Recurrence of synechiae and subsequent re-closure of the angle remains a challenge after intervention, especially in higher risk eyes with a flaccid iris, thick tissue, or high iris insertion. Furthermore, some eyes, even after laser or surgical angle opening, remain with elevated IOP implying an underlying open angle mechanism as well. This may be due to prior chronic apposition or PAS causing structural TM and Schlemm’s canal damage.¹¹

Pupil cerclage is a local and continuous running circle suture technique placed at the pupil margin that has been previously described in the literature as a method to address atonic mydriatic pupils.^12–15 In ACG eyes, we have found that pupil cerclage improved angle widening and prevented PAS reformation likely due to centripetal tension on the iris. We previously described peripheral iris cerclage (PIC) as a modification of this approach, in which the running suture is placed more peripherally rather than centrally (Figure 1) to enhance local angle opening and prevent PAS reformation while preserving physiologic pupil function.¹² Furthermore, although still speculative, we also hypothesized that by pulling on the scleral spur due to the centripetal iris traction, this would increase the trabecular effective filtration area which may provide further IOP lowering via an open angle mechanism.¹² Recently, a case of neovascular ACG managed with GSL, trabecular micro-bypass stent implantation, and iris cerclage, aiming to prevent recurrent synechiae formation, was reported.¹⁶ The purpose of this study is to describe our novel surgical technique further with clinical and anatomical angle outcomes in patients with ACG.

Figure 1.

A schematic showing the placement of the suture for peripheral iris cerclage. A continuous, equidistant 360° 10–0 polypropylene suture is passed through the mid-peripheral iris stroma, or approximately 2 mm from the iris root around the pupillary margin. The blue outline indicates the course of the polypropylene suture.

Methods

This is a single-center, retrospective pilot study of consecutive cases describing our surgical technique for PIC. The study was conducted in accordance with the tenets of the Declaration of Helsinki. Institutional Review Board approval was obtained from the University of Toronto Research Ethics Board (#49334). All surgeries were performed by two surgeons practicing within an academic ophthalmology center in the Greater Toronto Area, Canada. Written informed consent for surgery was obtained from all patients. Baseline demographics included age, sex, laterality, ethnicity, and medical history. Baseline ophthalmic data included visual acuity, intraocular pressure, glaucoma medication classes, glaucoma type, cup-to-disc ratio, visual field mean deviation, and history of ocular surgery. Anterior segment optical coherence tomography (AS-OCT) was performed using ANTERION (Heidelberg Engineering, Heidelberg, Germany), and ultrasound biomicroscopy (UBM) was performed using VuMax HD (Sonomed Escalon, Lake Success, New York, United States), to assess anterior chamber angle structures before and after surgery.

Inclusion and Exclusion Criteria

Patients were included if they had undergone a PIC at our centre between 2010 and 2025 with at least 1 month of follow-up. Eligible participants were adults aged 18 years or older with a diagnosis of angle-closure glaucoma who underwent peripheral iris cerclage. Eyes selected for adjunctive PIC were considered at high risk for persistent postoperative angle closure or reformation of PAS due to plateau iris syndrome (PIS), high iris insertion, or flaccid irides with lens extraction alone or had recurrent angle closure after phacoemulsification. The mechanism of angle closure was assigned based on the overall clinical assessment, including gonioscopy, anterior segment imaging, and surgeon judgment. Gonioscopy was performed by the treating glaucoma surgeons using four-mirror gonioscopy under low illumination, Combined surgeries involving goniosynechialysis, endocycloplasty (180° of treatment), or minimally invasive glaucoma surgery (MIGS) were included.

Surgical Technique

PIC was performed as one of the last steps of the surgery. An intracameral miotic was injected into the anterior chamber to achieve maximal pupillary constriction. Four 1 mm incisions were made at 3, 6, 9, and 12 o’clock positions. Figure 1 shows a schematic of the placement of the suture for peripheral iris cerclage. A 10–0 polypropylene suture on a CIF-4 needle (Ethicon, Raritan, New Jersey, United States) was used to pass through the peripheral iris, approximately 2 mm from the iris insertion. The needle was oriented parallel to the angle, and 2 to 3 full-thickness basting type suture passes were made per quadrant, each 2 mm long (Figure 2A–D). All four quadrants were addressed sequentially, with the suture needle emerging out and then back in through the same corneal incision, ensuring a complete cerclage. After completing the full 360° pass, both ends of the suture were externalized through one of the corneal incisions (Figure 2E) and tightened until sufficient iris was seen gathering at the basting sites (Figure 2F). This ensured adequate peripheral tension of the iris insertion into the angle. The knot was finalized using a McAhmed (modified McCannel) technique and trimmed with micro-scissors.

Figure 2.

A 10–0 polypropylene suture on a CIF-4 needle (Ethicon) is passed 2 mm from the iris insertion. (A–D) The needle is advanced sequentially through the inferonasal (A), inferotemporal (B), superonasal (C), and superotemporal (D) quadrants. In each quadrant, two to three robust bites of iris stroma are taken to complete a 360° cerclage. Both suture ends are then externalized through the main temporal incision. (E) The arrow indicates the position of the suture. The suture is tied with gentle but adequate tension to constrict the midperipheral iris, thereby aiding in opening of the iridocorneal angle (F).

Postoperatively, topical steroids were used every 2 hours for the first week and then tapered over the next several weeks. Glaucoma drops were continued in the early postoperative period and then tapered down if the IOP improved.

Outcome Measures

The primary outcome was the change in angle opening and extent of PAS after PIC. Shaffer grade and extent of PAS were recorded by quadrants, gonioscopically with a four-mirror lens under low illumination.

Secondary outcomes included the proportion of eyes achieving surgical success postoperatively, defined as IOP ≤18 mmHg with ≥20% reduction from baseline, without clinical hypotony (IOP <6 mmHg accompanied by ≥2-line loss of visual acuity from baseline). Complete success met the criteria without glaucoma medications, while qualified success permitted the use of glaucoma medications. Eyes that underwent surgical revision, reoperation or developed no light perception (NLP) vision were classified as immediate failures.

Additional outcomes included changes in IOP, glaucoma medication use, and corrected distance visual acuity (CDVA). Postoperative interventions, complications, and any surgical revision or reoperation were also recorded. All postoperative outcomes represent the latest available follow-up visit for each eye.

Statistical Analysis

Continuous variables were summarized as mean ± standard deviation or as median with interquartile range, according to distribution. Categorical variables were reported as counts and percentages and compared with chi-square or Fisher exact tests. A paired two-sided t-test was used for parametric data, and the Wilcoxon signed-rank test was used for nonparametric data. All visual acuities were converted from Snellen to the logarithm of the minimum angle of resolution (logMAR). P value < 0.05 was considered statistically significant.

Results

Study Population and Baseline Characteristics

A total of 8 eyes (7 patients) with angle-closure glaucoma underwent peripheral iris cerclage. Individual patient demographics are available in Table 1. Most eyes had a diagnosis of plateau iris syndrome and over half of the eyes (62.5%) were classified as advanced glaucoma. The median (IQR) axial length (AL) and anterior chamber depth (ACD) were 23.34 (23.03–23.83) mm and 3.11 (2.48–3.36) mm, respectively. Although these were all ACG eyes, both axial length and anterior chamber depth were within normal limits, as expected given that most eyes had plateau iris syndrome. Two eyes were pseudophakic (25%), and 3 eyes (37.5%) had previously undergone laser peripheral iridotomy.

Table 1.

Baseline Demographics and Ocular Characteristics

Patient No.	Age	Sex	Ethnicity	Laterality	Mechanism of Angle-Closure	Combined Procedures	Past Procedures	Cup-to-Disc Ratio	Preoperative VF MD, dB	Axial Length, mm	Anterior Chamber Depth, mm
1	72	F	South Asian	OD	Plateau iris	GSL, Trabecular Bypass Stent, Goniotomy	CEIOL	0.4	−5.68	24.02	3.46
2a	40	F	African	OD	Plateau iris	CEIOL, Trabecular Bypass Stent, Goniotomy	None	0.99	−27.11	23.35	3.51
2b	40	F	African	OS	Plateau iris	CEIOL, Goniotomy, Trabecular Bypass Stent, ECPL	None	0.99	−29.17	23.29	3.49
3	55	M	East Asian	OD	Plateau iris	CEIOL, GSL	SLT	0.9	−15.00	27.03	3.25
4	50	F	Caucasian	OD	Plateau iris	GSL	CEIOL, GSL	0.3	−6.81	21.38	3.11
5	54	M	Southeast Asian	OD	Plateau iris	CEIOL, GSL, ECPL, Trabecular Bypass Stent, Goniotomy	LPI	0.8	−12.19	23.32	2.51
6	57	M	Middle Eastern	OD	Pupillary block, flaccid iris	CEIOL, ECPL, GSL, Trabecular Bypass Stent, CTR	LPI	0.6	−2.06	23.76	2.45
7	50	F	South Asian	OD	Pupillary block, flaccid iris	CEIOL, GSL, Goniotomy, Trabecular Bypass Stent,	LPI	0.8	−24.85	22.25	2.15

Note: Patients 2a and 2b represent the right and left eyes of the same patient.

Abbreviations: CEIOL, cataract extraction with intraocular lens implantation; GSL, goniosynechialysis; ECPL, Endoscopic Cycloplasty; SLT, selective laser trabeculoplasty; LPI, laser peripheral iridotomy; CTR, capsular tension ring; VF MD, Visual Field Mean Deviation.

All patients underwent peripheral iris cerclage as an adjunctive surgical procedure. Cataract surgery (87.5%) and trabecular bypass stenting (75%) were among the most common adjunct procedures. Median (IQR) follow up time was 24.5 (16.8–37.8) months.

Figure 3 demonstrates the postoperative appearance following PIC, showing constriction of the peripheral iris with preservation of a well-centered pupil and a smooth, regular margin.

Figure 3.

Slit-lamp photograph demonstrating the postoperative appearance of peripheral iris cerclage, with constriction of the peripheral iris and maintenance of a well-centered pupil with a smooth, regular margin. Arrows indicate examples of the suture placement for the iris cerclage along the mid-peripheral iris.

Angle Grading and Peripheral Anterior Synechiae

Clinical outcomes are listed in Table 2 and summarized in Table 3. Median (IQR) Shaffer grade increased significantly from 0 (0–0) preoperatively to 3 (3–3) postoperatively, with significant angle widening (p = 0.01). Most eyes had PAS in at last one quadrant preoperatively, and all eyes showed a reduction of PAS postoperatively (p = 0.03). Six of 8 eyes had no PAS postoperatively. AS-OCT and UBM were used qualitatively to assess postoperative anterior segment anatomy. In all eyes, imaging demonstrated a thinner peripheral iris with a flatter profile and open angles in all quadrants. Representative images are shown in Figures 4 and 5.

Table 2.

Patient-Specific Clinical Outcomes Following Peripheral Iris Cerclage

Patient No.	Follow-Up, Months	Pre-Operative						Post-Operative
		IOP, mmHg	Classes, No.	Oral CAI	CDVA, Snellen	Schaffer Grade	PAS Quadrants, No.	IOP, mmHg	Classes, no.	Oral CAI	CDVA, Snellen	Schaffer Grade	PAS Quadrants, No.	IOP Reduction, %	Complete Success*	Qualified Success†
1	30	28	4	0	20/25	0	3	18	3	0	20/40	4	0	35.7	N	Y
2a	37	29	4	1	20/25	0	2	11	1	0	20/20	3	0	62.1	N	Y
2b	40	32	3	1	20/500	0	2	10	1	0	20/160	2	0	68.8	N	Y
3	9	48	4	1	CF	0	1	14	4	1	CF	2	1	70.8	N§	N§
4	17	42	5	1	20/40	0	3	10	0	0	20/25	3	0	78.0	Y	Y
5	16	34	4	1	20/20	0	1	13	2	0	20/20	3	0	61.7	N	Y
6	19	33	4	0	20/20	0	4	18	4	0	20/25	3	1	45.4	N	Y
7	43	58	3	0	20/20	0	0	10	0	0	20/20	3	0	82.8	Y	Y

Notes: Surgical success was defined as IOP ≤18 mmHg and ≥20% reduction from baseline at last follow-up visit. Complete success (CS)* met these criteria without glaucoma medications; qualified success (QS)^† met them with medications. Failure was defined as IOP <6 mmHg with ≥2-line loss of visual acuity from baseline, reoperation, or no light perception vision. ^§Patient was considered a failure due to re-operation. Patients 2a and 2b represent the right and left eyes of the same patient.

Abbreviations: IOP, intraocular pressure; CAI, carbonic anhydrase inhibitor; CDVA, corrected distance visual acuity; PAS, peripheral anterior synechiae; IQR, interquartile range; OD, right eye (oculus dexter); OS, left eye (oculus sinister).

Table 3.

Summarized Clinical Outcomes Following Peripheral Iris Cerclage

Outcome	Pre-Operative	Post-Operative	p-value
Shaffer grade, median (IQR)	0 (0–0)	3 (3–3)	0.01
PAS extent (quadrants), no.(%)			0.03
0 quadrants	1 (12.5)	6 (75)
1 quadrant	2 (25)	2 (25)
2 quadrants	2 (25)	0
3 quadrants	2 (25)	0
4 quadrants	1 (12.5)	0
IOP, mmHg, median (IQR)	33.5 (31.2–43.5)	12.0 (10–15)	0.01
IOP reduction, %, median (IQR)	–	65.4 (53.6–74.4)
Medication classes, median (IQR)	4 (4–4)	2 (1–3)	0.04
Oral CAI use, no. (%)	5 (62.5)	0
LogMAR CDVA median (IQR)	0.13 (0.02–0.60)	0.06 (0.02–0.49)	0.42
Complete success*, no. (%)	–	2 (25)
Qualified success†, no. (%)	–	7 (87.5)

Notes: Surgical success was defined as IOP ≤18 mmHg and ≥20% reduction from baseline at latest follow-up. Complete success (CS)* met these criteria without glaucoma medications; qualified success (QS)^† met them with medications. Failure was defined as IOP <6 mmHg with ≥2-line loss of visual acuity from baseline, reoperation, or no light perception vision.

Abbreviations: IOP, Intraocular pressure; IQR, interquartile range; CDVA, corrected distance visual acuity; logMAR, logarithm of the minimum angle of resolution; CAI, Carbonic Anhydrase Inhibitor; PAS, peripheral anterior synechiae; F, female; M, male; OD, right eye (oculus dexter); OS, left eye (oculus sinister); VF MD, Visual field mean deviation.

Figure 4.

Anterior segment optical coherence tomography images from patient 2, who underwent bilateral peripheral iris cerclage (A and B) right eye: (A) preoperative image showing angle closure with a plateau iris configuration; (B) postoperative image from the same eye. (C and D) left eye: (C) preoperative image; (D) postoperative image from the same eye. Both eyes show thinning of the peripheral iris and opening of the angle postoperatively.

Figure 5.

Ultrasound biomicroscopy images obtained preoperatively and postoperatively. (A) Preoperative image from patient 4. (B) Postoperative image from the same patient demonstrating thinning of the peripheral iris and opening of the angle following peripheral iris cerclage. (C) Preoperative image from patient 5. (D) Postoperative image from the same second patient showing thinning of peripheral iris and opening of the angle.

Surgical Success, Intraocular Pressure, Medications, and Visual Acuity

At the latest postoperative visit, 2 of 8 eyes (25%) achieved complete success and 7 of 8 eyes (87.5%) achieved qualified success, meeting the surgical success criteria of IOP 6 to 18 mmHg with a ≥20% reduction from baseline. At the time of surgical decision, the median (IQR) IOP was 33.5 (31.2–43.5) mmHg, which significantly decreased to 12 (10–15) mmHg post-operatively (p = 0.01). The median (IQR) percent reduction in IOP was 65.4% (53.6–74.4) postoperatively. The number of glaucoma medication classes also decreased, from a median (IQR) of 4 (4–4) pre-operatively to 2 (1–3) post-operatively (p = 0.04). Figure 6 shows a scatterplot of pre and postoperative IOP and meds. Median (IQR) logMAR CDVA was 0.13 (0.02–0.6) pre-operatively did not significantly change and 0.06 (0.02–0.49) post-operatively (p = 0.42). No eyes lost more than one line of visual acuity.

Figure 6.

Scatterplot comparing preoperative and postoperative intraocular pressure (IOP). Colours indicate the number of postoperative glaucoma medication classes. Data points on the dotted line represent no change in IOP compared with preoperative IOP, whereas points below the line represent a reduction in IOP.

Adverse Events, Interventions and Reoperations

There were no intraoperative complications. Postoperatively, three eyes experienced elevated IOP (>30 mmHg) on postoperative day one, two of which required anterior chamber paracentesis. One patient developed corneal edema which resolved by month 5, and another had persistent uveitis resolving by month 6. In one eye, a membrane developed over the pupil in the early postoperative period, which resolved after Nd:YAG laser membranectomy at month 3. One eye experienced a PIC-related complication, with a broken cerclage suture identified in the early postoperative period. The IOP remained uncontrolled postoperatively, requiring maximal medications including an oral CAI. Although the IOP reduced from 48 to 14 mmHg, the patient became intolerant to the oral CAI and thus subsequently, underwent microinvasive bleb surgery, achieving IOP control.

Discussion

This pilot study describes the use of peripheral iris cerclage as an adjunctive procedure in the management of ACG in eyes at high risk for PAS reformation. PIC creates continuous, uniform peripheral centripetal traction that pulls the iris away from the angle with minimal impact on central iris and pupil function. The primary goal is to reduce the risk of PAS formation as well as potentially enhance conventional outflow. This mechanism is akin to the effect of pilocarpine, which pulls the iris away from the angle, promotes angle opening, and lowers IOP through increased trabecular outflow.

Patients in our study were a difficult to treat population, which included eyes with very high IOP on maximal medical therapy (with the majority on an oral carbonic anhydrase inhibitor), advanced glaucoma, recurrent PAS, and in some cases failed prior surgical intervention. These eyes were at high risk for persistent postoperative angle closure or reformation of PAS due to plateau iris syndrome, high iris insertion, or flaccid irides. After treatment with adjunctive PIC, all eyes maintained open angles postoperatively with resolution of PAS. This is further substantiated by the dramatic reduction in IOP (65%), postoperative IOP (34 to 12 mmHg) and medication count (4 to 2).

Conventional surgical strategies for ACG focus on relieving pupillary block with laser iridotomy or rotating the iris posteriorly to open the angle with lensectomy. While these approaches can be effective in early or acute disease, they are often insufficient in eyes with extensive or chronic PAS, plateau iris configuration, or flaccid iris tone, where postoperative angle closure, synechiae reformation, and combined mechanism open angle glaucoma remain common. Although the EAGLE trial¹⁷ demonstrated superior outcomes with initial clear-lens extraction compared to LPI, lens extraction alone is often insufficient in eyes with extensive or chronic PAS.¹⁸ Tham et al¹⁰ reported 20% of patients requiring trabeculectomy after phacoemulsification for medically uncontrolled ACG and this rate went up to 32% in other series.¹⁹ Combining GSL can restore angle anatomy and improve outflow,^18,20–25 but its IOP-lowering effect may be limited by underlying trabecular dysfunction and PAS recurrence.^22,24 Tian et al²⁶ reported a high rate of PAS recurrence after cataract extraction combined with GSL, particularly in chronic angle-closure compared with acute angle closure (83.3% vs 30%, P = 0.01). These findings highlight the need for adjunctive strategies, such as PIC, that may help reduce the risk of synechiae reformation and/or enhance conventional trabecular outflow.

A distinguishing feature of our study population is the high prevalence of plateau iris syndrome. This condition responds less favorably to phacoemulsification alone than pupillary block because, although lens extraction can widen the angle and reduce anterior positioning of the ciliary process,²⁷ it does not address iridociliary apposition.^28,29 Miotic agents^30,31 and argon laser peripheral iridoplasty (ALPI)^32,33 remain the standard treatments for plateau iris by mechanically retracting the peripheral iris and widening the angle and Schlemm’s canal. However, they are often limited by variable efficacy^30,31 and lack of long-term durability.^32–35 Endocycloplasty is a newer treatment option for plateau iris syndrome, but long-term data has shown that combined cataract surgery and 360° ECPL achieved only a modest IOP reduction in patients with uncontrolled glaucoma and nearly 60% of eyes were classified as failures.³⁶

Iris cerclage can maintain angle patency by exerting persistent centripetal tension on the peripheral iris, acting as a circumferential tether, potentially reducing the recurrence of synechiae formation and/or the need for more invasive glaucoma procedures.^12–16 Centripetal tension recesses the peripheral iris from the trabecular meshwork, widens the angle with reduced PAS, and stabilizes the iris.^12,15,16 Peripheral iris cerclage offers a practical advantage over traditional cerclage and pilocarpine, because physiologic pupillary dilation is preserved for the most part. This avoids reduction of scotopic vision and allows for adequate evaluation of the posterior segment.

Although multiple adjunctive procedures were performed across the eight eyes in this study, making it difficult to isolate and attribute the observed outcomes specifically to PIC, clinical findings and anterior segment imaging suggest that these additional interventions alone would be unlikely to have achieved the degree of sustained angle opening and PAS prevention observed. A recent meta-analysis⁶ evaluating phacoemulsification combined with GSL and various MIGS procedures reported IOP reductions ranging from 3.94 to 13.10 mmHg. Similarly, studies of phacoemulsification combined with endocycloplasty and GSL have reported IOP reductions of approximately 9.5–9.9 mmHg.³⁷ In contrast, the present study demonstrated a substantially greater mean IOP reduction of 19.0 mmHg. Moreover, prior studies involving multiple combined procedures consistently report postoperative PAS reformation, whereas no PAS recurrence was observed during the follow-up period in this cohort.^37–39

In primary angle-closure glaucoma (PACG), obstruction of aqueous outflow due to iris apposition may cause swelling and degeneration of trabecular cells and endothelial damage of Schlemm’s canal (SC).^40–43 Hamanaka et al¹¹ found this leads to persistent SC occlusion and fusion of the trabecular beam, which can be worse in the presence of PAS and can persist even after reopening the angle. This “combined mechanism” scenario can lead to persistent elevated IOP even after angle opening in ACG.

We hypothesize that PIC may also enhance conventional outflow (and thus address combined mechanism glaucoma) by exerting centripetal traction on the iris root and pulling the scleral spur posteriorly. This may mechanically rotate the trabecular beams, open Schlemm’s canal, and improve aqueous outflow, similar to the effect of pilocarpine-induced ciliary muscle contraction.^30,31,44 Notably, this is based on the intimate anatomical relationship between the iris root, ciliary muscle, the trabecular meshwork and Schlemm’s canal^11,44,45 when the ciliary muscle contracts in response to muscarinic cholinergic agonist drugs, the meshwork expands, relaxes, and becomes less stiff, while Schlemm’s canal dilates, increasing outflow facility and reducing IOP.^44,46 Notably, although eyes in our study were at risk for combined mechanism glaucoma post-angle opening, most eyes in our study had a profound drop in IOP, with some even below 13 mmHg, suggesting an effect beyond simply opening the angle. If confirmed, this mechanism raises the possibility that PIC could exert a hypotensive effect in open-angle glaucoma (OAG) as well, warranting further investigation.

Interestingly, the one eye that required a secondary surgical intervention had a broken cerclage suture, potentially negating the effect on conventional outflow and leading to loss of IOP control. Although speculative, this observation may provide indirect support for the proposed mechanistic hypothesis underlying the procedure, whereby sustained centripetal traction enhances conventional aqueous outflow through mechanical expansion of the trabecular outflow pathway.

Peripheral iris cerclage may be especially beneficial for eyes that have previously undergone interventions yet continue to experience recurrent PAS with associated IOP elevation. Additionally, it may be considered as primary adjunctive procedure in angle-closure eyes at increased risk, such as eyes with extensive and chronic PAS, plateau configuration, flaccid irides, and/or resistance to medication.^47–49 Wang et al⁴⁷ identified the use of multiple preoperative IOP-lowering medications and larger residual PAS extent to be independent risk factors for extensive postoperative PAS. PAS reformation after phaco-GSL often exceeds 50%, reaching up to 80% in eyes with near-circumferential involvement.⁴⁹ The likelihood of recurrence increases further surpassing 80% in chronic disease²⁶ and 70% in plateau iris configuration.⁴⁹ In our series of PIC we had no cases of PAS recurrence.

A strength of this study is that we included consecutive eyes and the relatively long follow-up of approximately 24 months. Because PAS reformation most commonly occurs in the early postoperative period, sustained angle opening beyond this window supports the durability of the observed anatomical outcomes.^18,26 Additional strengths include the integration of a clearly described surgical technique with clinical outcomes, detailed gonioscopic evaluation, and anterior segment imaging, allowing for objective documentation of angle opening and synechial resolution.

This study has several limitations, including its retrospective design, small sample size, inclusion of both eyes from one patient with potential inter-eye correlation, absence of a control group (eg, phacoemulsification alone), and potential confounding from the various adjunctive procedures performed. Nonetheless, patient 4 within this series provides a relatively isolated assessment of PIC independent of cataract extraction or trabecular bypass stenting. This patient had previously undergone phacoemulsification and GSL; however, persistent PAS remained in the setting of plateau iris configuration. The patient subsequently underwent PIC with repeat GSL alone, resulting in IOP reduction from 42 mmHg to 10 mmHg (78% reduction) without glaucoma medications at 17 months. Although limited to a single case, this represents the strongest within-study example suggesting an effect attributable to PIC.

It is also important to note that this represents a highly selected and clinically challenging population, patients with angle-closure glaucoma refractory to primary interventions, and at high risk for recurrent PAS, making large cohorts difficult to assemble. Given the novelty of this technique, we felt a pilot study would be helpful as a proof of concept to inform future larger prospective research. Although a formal control group was not included, the included eyes had previously undergone phacoemulsification with persistent postoperative angle closure and PAS reformation but had a substantial improvement in angle opening and IOP after PIC. In contrast to previously reported PAS recurrence rates of up to 80% in similar populations, no PAS recurrence was observed in this series; however, these findings should be interpreted cautiously given the sample size and lack of controls. As a novel surgical technique, outcomes may also reflect surgeon experience and a procedural learning curve, which may limit broader adoption.

In conclusion, peripheral iris cerclage appears to be a promising adjunctive surgical strategy for selected eyes with angle-closure glaucoma at high risk for recurrent peripheral anterior synechiae, including those with plateau iris configuration, flaccid iris, or prior failed interventions. PIC should be considered a complementary angle-preserving technique intended to enhance anatomical outcomes and likely contribute to IOP reduction in selected high-risk eyes, potentially avoiding higher morbidity external drainage surgeries, especially in ACG. In this pilot study, adjunctive PIC was associated with sustained postoperative angle opening, absence of PAS reformation, and meaningful intraocular pressure reduction. PIC may also exert a potential open angle mechanism by traction on the scleral spur. These findings support larger prospective, controlled comparative studies to better define the independent contribution and the long-term role of PIC in angle-closure disease and to explore its potential applicability in open angle glaucoma.

Funding Statement

IIKA: Supported in part by an Unrestricted Grant from Research to Prevent Blindness, New York, NY, to the Department of Ophthalmology & Visual Sciences, University of Utah. The sponsor or funding organization had no role in the design or conduct of this research.

Disclosure

C – Consultant/Consulting Fees; S – Speakers Honoraria; R – Research Grant/Support. Iqbal Ike K. Ahmed: Abbvie: C; Aliph Medical: C; Ace Vision: C; Aequus: C; Amaros Engine: C; Apellis Pharmaceutical: C; Aerie Pharmaceuticals: C,R; Akorn: C; Alcon: C,S,R; Allergan: C,S,R; Aquea Health, Inc.: C; ArcScan: C; Avellino Lab USA: C; Avisi: C; Balance Ophthalmic: C; Bausch Health: C; Beaver Visitec: C; Belkin Vision: C; Beyeonics: C; Bionode: C,R; Ciliatech: C: Carl Zeiss Meditec: C,S; Centricity Vision, Inc.: C; CorNeat Vision: C; Custom Surgical: C; Dragonfleye Therapeutics: C; Emmes Biopharma: C; Eye to Eye TeleHealth: C; EyeX Solutions: C; Elios Vision: C; ElutiMed: C; Equinox: C; eyeFlow, Inc.: C; EyedMed: C; EyeQ Technologies: C; Exhaura Limited: C; Genentech: C; Glaukos: C,R; Gore: C; Heine: C,S; Heru: C; Hexiris Pharma: C; Implandata: C; iCare: C; Iantrek: C; InjectSense: C; Iridex: C; iStar: C; Ivantis: C,R; Johnson & Johnson Vision: C,S,R; Liqid Medical: C; Labtician Théa: C; LayerBio: C; Leica Microsystems: C; Life Long Vision: C; Long Bridge Medical, Inc.: C; Medicontur: C; MicroOptx: C; MST Surgical: C,S; Myra Vision/Shifamed LLC: C; Noxelis: C; New World Medical: C,R; Nova Eye: C; Ocular Instruments: C; Ocular Therapeutix: C; Oculo: C; Oculus Surgical: C; OcuSciences: C; Omega Ophthalmics: C; Ophthalmic Therapeutic Innovations: C; Orbitau: C; Perfuse Therapeutics: C; Peripherex: C; PolyActiva: C; PulseMedica: C; Qlaris Bio: C; Regeneron Pharmaceuticals, Inc: C; Radiance Therapeutics, Inc.: C; Radius XR: C; Rheon Medical SA: C; Ripple Therapeutics: C; SeonixBio: C; Sierra Clinical Services: C; Shifamed: C; Shockwave Medical: C; Samsara Vision: C; Sanoculis: C; Santen: C,R; Singapore Biodesign Programme Office: C; Sight Sciences: C; Smartlens, Inc.: C; Stroma: C; Tavo Biopharma: C; Thea Pharma: C; TFS Health Science: C; Visci Ltd: C; ViaLase: C; Visus Therapeutics: C; Vizzario: C; VSY Biotechnology: C; Zilia, Inc.: C. Ticiana De Francesco: Alcon: C; Allergan: C,S; Glaukos Corp: C,S; Sight Sciences Inc: C; Elios: C; Myra Vision: C; Iantrek: C; Carl Zeiss Meditec AG: C; Vialase: C; Nova Eye Medical: C; Thea Pharma: S; Implante Plano Miranda: R. Ticiana De Francesco: Alcon (Geneva, Switzerland): consultation; Allergan (Dublin, Ireland): consultation, honoraria; Glaukos Corp (San Clemente, California, USA): consultation, honoraria; Sight Sciences Inc (Menlo Park, California, USA): consultation; Elios; Consultation; Myra Vision: consultation; Iantrek: consultation; Carl Zeiss Meditec AG: consultation; Vialase: consultation; Nova Eye Medical: consultation; Thea Pharma: honorarium. Implante Plano Miranda: writing support. The authors report no other conflicts of interest in this work.