This multicenter, retrospective cohort study involved consecutive patients who underwent PMS implantation between August 2022 and June 2024 at Kyoto Prefectural University of Medicine, Kyoto, Japan, and its affiliated hospitals, and at the Fukushima Eye Clinic, Osaka, Japan. Ethical approval for this study was obtained from the Institutional Review Board (approval no. ERB-C-1909-2), and the study was conducted in accordance with the tenets outlined in the Declaration of Helsinki. Written informed consent for the surgical procedure was obtained from all participants before their involvement in the study. Eligible eyes required at least 3 months of postoperative follow-up; patients younger than 18 years and those lost to follow-up before the 3-month postoperative visit were excluded.

Demographic and clinical data were collected from the medical records of all subjects, including age, sex, laterality, glaucoma subtype, preoperative best-corrected visual acuity (BCVA), IOP, number of glaucoma medications used, central corneal thickness, axial length, and visual field mean deviation. Moreover, information on previous intraocular procedures (glaucoma surgery, cataract surgery, or vitrectomy) and surgical details (stand-alone PMS or PMS combined with cataract surgery), additional procedures (posterior part of the tube fixation or intraluminal suture stenting), and duration of MMC exposure (3 minutes or 5 minutes) was also recorded.

In all patients, IOP was assessed using a Goldmann applanation tonometer. Medication scores were calculated from the number of glaucoma therapies: each single-agent eyedrop counted as 1 point, each fixed-combination eyedrop as 2 points, and oral acetazolamide as 1 point per tablet.

All surgeries were performed by six experienced glaucoma specialists using a standardized PMS implantation technique. Briefly, after placement of a corneal traction suture, a superior fornix-based conjunctival peritomy was created, followed by careful dissection of the Tenon’s capsule. MMC (0.4 mg/mL) was then applied to the exposed sclera using cellulose sponges for either 3 or 5 minutes according to each institutional protocol, after which the area was thoroughly irrigated with saline solution. Next, a scleral track was fashioned with a dedicated double-step knife at a point 3 mm posterior to the limbus to allow insertion of the PMS device into the anterior chamber. The fins of the PMS were then securely positioned within the scleral tunnel, and adequate flow of aqueous humor through the distal end was confirmed. Tenon’s capsule and conjunctiva were then closed with interrupted 10-0 nylon sutures. At the end of surgery, a subconjunctival corticosteroid injection was administered, and patients were prescribed a standard postoperative regimen of topical corticosteroids and antibiotics.

At the discretion of the operating surgeon, additional procedures were undertaken to optimize surgical outcomes. These included intraluminal suture stenting to modulate aqueous outflow during the early postoperative period, a technique previously described as an adjunctive measure to improve surgical safety. ^, Posterior fixation of the device was also performed to prevent tube migration or elevation, as reported in our prior work. Intraoperative images of these additional procedures are shown in Supplemental Figure 1.

In accordance with World Glaucoma Association guidelines, we applied three composite criteria for surgical success. Criteria A, B, and C were defined as an IOP of ≤ 18, of ≤ 15, and of ≤ 12 mm Hg, respectively, each combined with a ≥ 20% reduction from baseline. Outcomes were categorized as a complete success (CS) if the criterion was achieved without the need for any IOP-lowering medications, and as a qualified success (QS) if the criterion was achieved with or without the use of IOP-lowering medications.

Failure was defined as any of the following: (1) not meeting the prespecified IOP criterion at two consecutive follow-up visits at least 1 month apart and occurring more than 1 month after surgery; (2) the need for an additional glaucoma surgery to control elevated IOP or to address severe hypotony-related complications; or (3) loss of light perception. Bleb needling and minor surgical revisions performed for bleb dysesthesia or persistent bleb leakage without hypotony were not considered surgical failures and were instead recorded as postoperative interventions. For IOP-based failures, the failure date was assigned to the first of the two consecutive follow-up visits, whereas for failures requiring additional surgery, the failure time was recorded as the date of the reoperation.

Postoperative complications and subsequent surgical interventions were prespecified as safety outcomes. Complications included hypotony, hyphema, and any other adverse event postsurgery. Hypotony was defined as an IOP of ≤ 5 mm Hg, and hypotony-related manifestations included a shallow anterior chamber, choroidal detachment, and hypotony maculopathy. A shallow anterior chamber was defined as a marked reduction in anterior chamber depth as assessed by slit-lamp examination. Hyphema was characterized as a visible hemorrhage sediment in the anterior chamber on slit-lamp examination. Early postoperative IOP elevation was defined as an IOP of ≥ 30 mm Hg within 1 month after surgery.

All additional surgical procedures performed after PMS implantation were recorded, including further filtering or drainage device surgeries, surgical bleb revisions, and other interventions undertaken to manage complications such as severe hypotony or malignant glaucoma. Both the type and timing of each reoperation were documented for analysis.

Baseline characteristics were summarized as median values with an IQR (IQR) for continuous variables and as counts with percentages for categorical variables. Changes in IOP and medication scores from baseline to postoperative time points were assessed using linear mixed-effects models with patient identifier included as a random intercept to account for within-patient correlation due to the inclusion of both eyes from some patients. For longitudinal analyses of IOP and medication scores, postoperative measurements obtained after additional glaucoma surgery performed for elevated IOP or severe hypotony-related complications were excluded.

Surgical outcomes were analyzed with Kaplan–Meier survival curves for qualified and complete success according to Criteria A, B, and C. All survival analyses were restricted to events occurring within 12 months postoperatively, with eyes censored at 12 months or at the last available follow-up, whichever came first. Multivariable Cox proportional hazards regression was used to evaluate factors associated with surgical failure, with patient-level clustering accounted for using a robust sandwich variance estimator. The included covariates were patient age, preoperative IOP, preoperative medication scores, central corneal thickness, axial length, glaucoma subtype, previous intraocular surgery, surgical type, additional procedures, and the 0.4 mg/mL MMC exposure time.

All statistical analyses were performed using R software version 4.3.3 (R Foundation for Statistical Computing). A P value of <.05 was considered statistically significant.

Of 719 consecutive patients (880 eyes) who underwent PMS implantation during the study period, 20 patients (24 eyes) were excluded due to the follow-up period in those patients being less than 3 months. Hence, this study included 699 patients ( N = 856 eyes). The median aged was 72 years (IQR, 64-79 years), and 48.1% were female. Primary open-angle glaucoma (POAG) was the most common diagnosis, followed by exfoliation glaucoma (XFG) and other secondary glaucoma. Among the other secondary glaucoma subtypes, the most frequent were uveitic glaucoma (34 eyes), neovascular glaucoma without active iris neovascularization (10 eyes), glaucoma after pars plana vitrectomy (9 eyes), and steroid-induced glaucoma (7 eyes). The median preoperative IOP was 18 mm Hg (IQR, 15-23 mm Hg) with a median of 4 medications (IQR, 3-5 medications). In regard to the surgical procedure, PMS implantation was performed as a stand-alone operation in the majority of eyes (77.5%). Posterior tube fixation was applied in 56.5% of the eyes, and intraluminal suture stenting in 18.7% of the eyes. MMC at a concentration of 0.4 mg/mL was applied for 3 minutes in 40.7% of the eyes, and for 5 minutes in 59.3% of the eyes. Baseline characteristics of the study population are outlined in Table 1 .

Postoperative IOP and medication scores are shown in Figure 1 . The median preoperative IOP was 18 mm Hg (IQR, 15-23 mm Hg), and markedly declined to 10 mm Hg (IQR, 8-11 mm Hg) at 1-month postoperative, 10 mm Hg (IQR, 8-12 mm Hg) at 2-months postoperative, 10 mm Hg (IQR, 9-12 mm Hg) at 3-months postoperative, 11 mm Hg (IQR, 9-13 mm Hg) at 6-months postoperative, and 11 mm Hg (IQR, 9-13 mm Hg) at 12-months postoperative. At all postoperative time-points, IOP remained significantly lower compared with that at baseline (all P <.001). The median medication scores were 4 (IQR, 3-5) preoperatively and decreased to 0 (IQR, 0-0) at every postoperative time-point through month 12, thus illustrating a sustained and significant reduction (all P <.001).

Violin plots showing intraocular pressure (IOP, left) and glaucoma medication scores (right) at baseline and follow-up visits up to 12-months postoperative. Each plot illustrates the distribution of values at each time-point, with the width of the violin plot reflecting the kernel density of the data distribution. The central diamond represents the mean value.

Kaplan–Meier success rates for QS and CS according to Criteria A, B, and C are shown in Figure 2 . Under Criterion A, survival probabilities at 6- and 12-month postoperative were 76.6% and 69.5%, respectively, for CS and 83.6% and 81.0%, respectively, for QS. Under Criterion B, survival rates at 6- and 12-month postoperative were 75.1% and 67.6%, respectively, for CS and 80.6% and 77.3%, respectively, for QS. Under the more stringent Criterion C, survival at 6- and 12-month postoperative was 64.6% and 59.4%, respectively, for CS and 67.5% and 66.0%, respectively, for QS.

Kaplan–Meier survival curves for surgical success according to three IOP criteria. Survival probabilities are shown separately for qualified success (solid lines) and complete success (dashed lines). The number of eyes at risk at each time-point is shown below each graph.

Multivariable Cox regression analysis of risk factors for failure to achieve CS is summarized in Table 2 .

TABLE 2

Multivariable Cox Regression Analysis of Risk Factors for Failure of CS.

Variable	Criteria A Failure		Criteria B Failure		Criteria C Failure
	HR (95% CI)	P Value	HR (95% CI)	P Value	HR (95% CI)	P Value
Age, years	0.97 (0.96-0.99)	<.001	0.97 (0.96-0.99)	<.001	0.97 (0.96-0.99)	<.001
Preoperative IOP, mm Hg	0.98 (0.96-1.01)	.194	0.99 (0.97-1.02)	.510	1.00 (0.98-1.02)	.863
Preoperative Medication scores, n	1.27 (1.15-1.40)	<.001	1.26 (1.15-1.39)	<.001	1.15 (1.05-1.26)	.003
Central Corneal thickness, µm	1.00 (1.00-1.00)	.623	1.00 (1.00-1.01)	.381	1.00 (1.00-1.01)	.203
Axial length, mm	0.95 (0.88-1.03)	.188	0.95 (0.88-1.03)	.213	0.97 (0.91-1.04)	.375
Glaucoma subtype (ref. POAG)
XFG	1.53 (1.08-2.18)	.017	1.39 (0.98-1.98)	.067	1.57 (1.16-2.13)	.003
SG	0.76 (0.44-1.31)	.321	0.82 (0.48-1.41)	.477	0.91 (0.55-1.50)	.717
PACG	0.60 (0.19-1.89)	.386	0.57 (0.18-1.79)	.338	0.52 (0.17-1.57)	.243
previous surgery
Outflow pathway–targeted surgery	0.59 (0.40-0.87)	.007	0.65 (0.45-0.94)	.022	0.74 (0.54-1.03)	.075
Filtering surgery	0.58 (0.33-1.02)	.057	0.61 (0.35-1.05)	.072	0.56 (0.33-0.95)	.032
Cataract surgery	2.84 (1.79-4.52)	<.001	2.90 (1.83-4.58)	<.001	2.77 (1.83-4.20)	<.001
Vitrectomy	0.73 (0.41-1.29)	.277	0.64 (0.36-1.14)	.126	0.61 (0.36-1.03)	.067
Surgical type
Combined with cataract surgery	3.29 (2.12-5.13)	<.001	3.24 (2.10-5.00)	<.001	3.06 (2.05-4.57)	<.001
Additional procedures
Posterior part of the tube fixation	0.57 (0.41-0.78)	<.001	0.61 (0.45-0.83)	.002	0.73 (0.56-0.95)	.018
Intraluminal suture stenting	0.61 (0.36-1.04)	.071	0.69 (0.41-1.14)	.143	0.80 (0.54-1.20)	.281
MMC Exposure time (3 Min)
5 Min	0.52 (0.37-0.72)	<.001	0.57 (0.41-0.78)	<.001	0.79 (0.60-1.04)	.093

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