Trabeculectomy and XEN45 gel stent implantation are glaucoma surgeries that creates an aqueous humor (AH) shunt towards the subconjunctival space (filtration bleb). Once the AH reaches the subconjunctival space, it is removed by different paths such as the trans-bleb wall route. For this reason, the conjunctiva is considered an essential structure that may condition the glaucoma filtering procedures outcomes. As part of the inflammatory response, an unbalanced fibrosis during the postoperative period may lead to a bleb cavity scarring and failure; for this reason, bleb massage and antifibrotic injections (i.e., 5-Fluoruracil) are frequently required as part of the postoperative care of these procedures. There have been described several risk factors, such as intraocular pressure (IOP) lowering medications, previous surgical interventions or ocular surface disease that may predispose to an early failure. These preoperative factors fail to aim to predict the surgical outcomes.
However, ocular biomarkers may overcome this limitation. There are promising studies that have analyzed the role of in vivo confocal microscopy (IVCM), anterior-segment optical coherence tomography (AS-OCT) and conjunctival cytology impression as clinical tools that may improve the filtration bleb assessment at a cellular level.
Detailed description Hypothesis
Objective
Design Single-center, prospective, simple-blind study
Primary outcomes All the outcomes are measured pre and postoperative at each follow-up time
Secondary outcomes
Sample size calculation Based on the most assessed outcome in glaucoma surgeries and the only pilot study aiming to determine a similar outcome, to detect IOP differences between both procedures that may reflect the surgical outcomes of both procedures and therefore reflect the subconjunctival changes, accepting an alfa risk of 0.05 and a beta risk of 0.20 in a two-sided Student's T-test, 40 subjects are necessary in each group to recognize as statistically significant a difference greater than or equal to - 13,38 mm Hg in IOP, with a common standard deviation of 17%. A drop-out rate of 15% has been anticipated. If no drop-out rate is considered, the number of needed subjects is 68 (34 per group)
Method Single center, prospective, observational study of primary open angle glaucoma and uncontrolled intraocular pressure, progression of the disease confirmed by visual field examination that require either XEN gel stent implantation or trabeculectomy.
Preoperative examinations
A specific case report form (CRF) was designed with all variables and data required for the study, including potential complications
Surgery. Patients were assigned either to trabeculectomy or XEN stent implantation
Trabeculectomy: the surgical technique is as follows: retro/peribulbar o subtenon's anesthesia, superior corneal traction suture, phacoemulsification through 2.2 with in-the-bag IOL implantation, a fornix-based conjunctival flap, sufficient but not excessive cauterization, application mitomycin-C (MMC) 0,2 mg/ml for 2 minutes under the conjunctiva, then MMC was washed out with 100 ml of saline solution, then a scleral flap (4x3 mm in the trabeculectomy) is dissected. A sclerectomy with punch and peripheral iridectomy were performed, and suture nylon 10/00 sutures was used to place 3 or 4 stiches in the scleral flap
XEN gel stent: a clear cornea incision in the inferotemporal quadrant was performed, injecting the XEN 45 device into the superonasal quadrant using an ab interno approach. Approximately 15 min before inserting the implant, 0.1 ml of a MMC solution (0.01%) was injected into the superior conjunctiva. Both stand-alone and combined phaco-glaucoma procedures were used.
Post-operative treatment. All patients instilled ofloxacin antibiotic every 6 hours for 1 week, dexamethasone (every 2 hours for 1 month, every 4-6 hours on the second month and tapered during the third month according to surgeon's instructions). Atropine was also used when clinical finds recommended its use. Subconjunctival injections of anti-fibrotic agents (5-FU) and/or bleb needling were allowed and performed at the discretion of the surgeon
Statistical analysis
| Condition | Ocular Hypertension, Ocular Hypertension, Glaucoma, Glaucoma, Glaucoma Open-Angle Primary |
|---|---|
| Treatment | trabeculectomy, XEN45 Gel stent |
| Clinical Study Identifier | NCT04727411 |
| Sponsor | Hospital Clinic of Barcelona |
| Last Modified on | 18 August 2022 |
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