Optimizing Graft Selection in Glaucoma Surgery: A Comparative Study of Sclera, Pericardium, and Corneal Tissue

Optimizing Graft Selection in Glaucoma Surgery

Glaucoma refers to a group of progressive optic neuropathies that lead to permanent vision loss. Glaucoma is the leading cause of irreversible blindness globally. In 2020, it was estimated to affect 76 million individuals worldwide, with projections indicating this number will rise to 111.8 million by 2040. In Canada, glaucoma affects an estimated 2.7-7.5% of individuals over the age of 50, contributing substantially to the national disease burden. This condition is linked to damage of the optic nerve due to elevated intraocular pressure (IOP; raised eye pressure), which results in the loss of retinal ganglion cells. Therefore, most of the treatments are guided towards reducing the IOP either via using laser, medications or surgery.

Glaucoma surgery is typically reserved for cases where IOP remains uncontrolled while on maximum tolerated medical therapy and/or where glaucoma progression warrants surgery. The goal of many glaucoma surgeries is to divert aqueous humor from the anterior chamber to the subconjunctival space, therefore reducing intraocular pressure. The device used for this purpose are the PRESERFLO™ MicroShunt (Glaukos Corporation, Laguna Hills, CA, USA) (the documents will interchangeably use terms "stent" and "shunt" to refer to these devices in the text below). The device is implanted using the ab externo approach to channel fluid from the anterior chamber to the subconjunctival/subtenon space. To reduce postoperative fibrosis and inhibit fibroblast activity that could obstruct flow and lead to device failure, 5-fluorouracil (5-FU) or mitomycin C (MMC) are administered. Additionally, a double-layered closure of conjunctiva and Tenon's is performed to minimize Tenon's migration and blockage of tenon the stents. Despite these measures, stent encapsulation and failure are still too common requiring revisions and bleb needling in 2-20% of cases within the first 12 months of follow-up.

This project will involve a series of studies evaluating graft selection in PreserFlo MicroShunt implantation, focusing on donor sclera, cornea, and pericardium as patch graft materials. First, the investigators will conduct a prospective, randomized study comparing clinical outcomes between these graft types. Outcomes of interest will include surgical success rates, post-operative hypotony, tube erosion, conjunctival complications, infection, and overall device longevity. Donor sclera has long been used as a patch graft in glaucoma drainage device surgery and is associated with low erosion rates and reliable long-term results. Corneal tissue is increasingly used due to its transparency and availability through eye banks, with demonstrated safety in ocular surface reconstruction and tube coverage. Pericardium is another durable, biocompatible option, historically applied in both cardiovascular and ocular surgery, and has shown effectiveness as a patch graft in glaucoma drainage implants. This comparison will extend to both primary implantation and revision surgeries, recognizing the high clinical relevance of graft performance in complex cases.

Building on these results, the investigators will then perform a cost-effectiveness analysis of graft strategies, incorporating surgical time, post-operative management, complication rates, and need for re-operation. An economic model will be developed to evaluate costs and resource utilization associated with each material, providing valuable data for policy and surgical decision-making. Finally, the investigators will conduct a patient-reported outcome (PRO) study to assess patient comfort and satisfaction with different grafts. Surveys will evaluate domains such as foreign body sensation, cosmesis, and overall satisfaction at key time points (immediate post-operative period, 1 week, 3 weeks, and 3 months). These results will highlight the patient perspective, an often underrepresented but critical factor in surgical innovation.

Together, these studies will comprehensively assess graft selection from surgical, economic, and patient-centered perspectives, informing evidence-based practice in glaucoma care.

Study Overview

• Status: Not yet recruiting
• Conditions: Glaucoma
• Intervention / Treatment: Procedure: MicroShunt with Scleral Patch Graft; Procedure: MicroShunt with Corneal Patch Graft; Procedure: MicroShunt with Pericardial Patch Graft

• Study Type: Interventional
• Enrollment (Estimated): 180
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Paige Campbell, MD; Phone Number: 14039695473; Email: pcampbe1@ualberta.ca

Study Locations

• Canada
  • Alberta
    • Edmonton, Alberta, Canada, T5H 3V9
      • The Royal Alexandra Hospital
      • Contact: Paige Campbell, MD; Phone Number: 4039695473; Email: pcampbe1@ualberta.ca
      • Principal Investigator: Mathew Palakkamanil, MD
      • Principal Investigator: Gurkaran Sarohia, MD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. Age 18 years and older
2. Patients selected for PreserFlo microshunt surgery and XEN stent alone or in combination with cataract surgery.
3. Ability to comprehend the study procedures

Exclusion Criteria:

1. Unwilling or unable to give consent
2. Unable to come for scheduled post-operative visits
3. Pregnant or nursing women
4. Previous cyclodestructive procedures, scleral buckling procedures, or presence of silicone oil
5. Conjunctival scarring precluding a glaucoma surgery superiorly
6. Active iris neovascularization or active proliferative retinopathy
7. Vitreous in the anterior chamber for which a vitrectomy is anticipated.
8. Previous trabeculectomy, tube-shunt implantation, or surgeries that shunt aqueous outflow into the subconjunctival space

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: PreserFlo with Donor Scleral Patch Graft; Participants undergo PreserFlo MicroShunt implantation with a donor scleral patch graft covering the tube. Standard perioperative care (e.g., MMC/5-FU per site protocol) and scheduled follow-up (day 1; week 1-2; months 1, 3, 6, 9, 12). Outcomes include IOP, hypotony, tube erosion, conjunctival complications, infection, reoperations, device longevity, patient-reported comfort/cosmesis, and resource use. Primary and revision cases are included per stratified randomization.	Procedure: MicroShunt with Scleral Patch Graft; Placement of PreserFlo MicroShunt with donor scleral patch graft to cover the tube.
Experimental: PreserFlo with Corneal Patch Graft; Participants undergo PreserFlo MicroShunt implantation with a donor corneal patch graft covering the tube. Standard perioperative care and identical follow-up schedule. Outcomes as above: IOP control, complications (including erosion and hypotony), reoperations, longevity, patient-reported outcomes, and resource use. Primary and revision cases are included per stratified randomization.	Procedure: MicroShunt with Corneal Patch Graft; Placement of PreserFlo MicroShunt with donor corneal patch graft to cover the tube.
Experimental: PreserFlo with Pericardial Patch Graft; Participants undergo PreserFlo MicroShunt implantation with a pericardial patch graft covering the tube. Standard perioperative care and identical follow-up schedule. Outcomes as above: IOP control, complication profile, reoperations, longevity, patient-reported outcomes, and resource use. Primary and revision cases are included per stratified randomization.	Procedure: MicroShunt with Pericardial Patch Graft; Placement of PreserFlo MicroShunt with pericardial patch graft to cover the tube.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Surgical Success Rate at 12 Months	Proportion of eyes achieving target IOP (≤18 mmHg or ≥20% reduction from baseline) without additional glaucoma surgery, vision-threatening complication, or device removal.	12 months
Mean Change in Intraocular Pressure (IOP) from Baseline to 12 Months	IOP measured by Goldmann applanation tonometry (mmHg) at baseline, post-operative Day 1, Week 1, Month 1, Month 3, Month 6, and Month 12. The primary endpoint will be the mean change at 12 months.	12 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Glaucoma medication burden	Number of glaucoma medications used per patient, counted from the medication list at each follow-up (baseline, Month 3, 6, 12). Outcome reported as: Mean change in number of medications.	12 months
Need for re-operation	Number and percentage of eyes requiring any additional glaucoma or device-related surgery during the study period. Outcome reported as: Count and proportion of eyes re-operated.	12 months
Bleb needling rate	Number and proportion of eyes requiring bleb needling postoperatively to maintain or restore filtration.	12 months
Tube/patch graft exposure or erosion	Clinically confirmed exposure or erosion of tube or patch graft, as documented on slit-lamp exam. Outcome reported as: Number and percentage of affected eyes.	12 months
Hypotony	IOP < 5 mmHg on two consecutive visits measured by Goldmann applanation tonometry (mmHg). Outcome reported as: Number and percentage of eyes meeting the definition.	12 months
Infection	Any endophthalmitis, blebitis, or wound infection confirmed on clinical exam. Outcome reported as: Number and percentage of eyes with infection.	12 months
Best-corrected visual acuity (BCVA) change	BCVA measured using a standard Early Treatment Diabetic Retinopathy Study (ETDRS) chart at 4 m (logMAR scale). Outcome reported as: Mean change in logMAR from baseline to 12 months (lower values = better vision).	12 months
Device survival (time to failure)	Time from surgery to defined surgical failure (loss of pressure control, device removal, or re-operation). Outcome reported as: Kaplan-Meier survival curve; median time to failure.	Up to 12 months
Patient-reported comfort	Measured using a Visual Analog Scale (VAS, 0-10) where 0 = no discomfort and 10 = worst possible discomfort. Assessment points: Post-op Day 1, Week 1, Week 3, and Month 3. Outcome reported as: Mean ± SD at each time point.	Immediate postop (day 1), 1 week, 3 weeks, 3 months.
Foreign body sensation	Evaluated using a Likert scale (1-5) where 1 = none and 5 = severe sensation. Assessment points: Day 1, Week 1, Week 3, Month 3. Outcome reported as: Mean ± SD and proportion reporting moderate-to-severe sensation (≥4).	Day 1, 1 week, 3 weeks, 3 months.
Cosmesis/satisfaction	Measured with a 5-point Likert scale assessing satisfaction with postoperative appearance (1 = very dissatisfied; 5 = very satisfied). Assessment points: Week 3 and Month 3. Outcome reported as: Mean ± SD; higher scores = greater satisfaction.	3 weeks and 3 months.
Health care resource use	Number of postoperative visits, additional procedures, and unscheduled urgent encounters recorded per participant from the medical record. Outcome reported as: Mean count per participant and associated cost estimate (CAD).	12 months
Cost-utility	Calculated using trial-based costs and quality-adjusted life-year (QALY) estimates derived from EQ-5D-5L utility weights. Outcome reported as: Incremental cost per QALY gained by graft type.	12 months

Collaborators and Investigators

• Sponsor: University of Alberta

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2026
• Primary Completion (Estimated): October 30, 2027
• Study Completion (Estimated): December 30, 2027

Study Registration Dates

• First Submitted: December 9, 2025
• First Submitted That Met QC Criteria: December 9, 2025
• First Posted (Actual): December 16, 2025

Study Record Updates

• Last Update Posted (Actual): March 19, 2026
• Last Update Submitted That Met QC Criteria: March 18, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: surgery; PRESERFLO; MicroShunt
• Additional Relevant MeSH Terms: Eye Diseases; Ocular Hypertension; Glaucoma
• Other Study ID Numbers: Pro00157655

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: Yes