Tube Versus Trabeculectomy (TVT) Study

Study Overview
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Brief Summary
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The purpose of the Tube Versus Trabeculectomy (TVT) Study is to compare the safety and efficacy of nonvalved tube shunt surgery to trabeculectomy with mitomycin C in patients with previous ocular surgery.

Detailed Description
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Glaucoma surgery is performed when further intraocular pressure (IOP) reduction is needed despite the use of maximum tolerated medical therapy and appropriate laser treatment. Trabeculectomy is generally used as the initial incisional surgical procedure in managing glaucoma. However, eyes in which trabeculectomy has failed are at greater risk of failure with subsequent filtering surgery. Wound modulation with antifibrotic agents, like mitomycin C (MMC) and 5-fluorouracil (5-FU), has been shown to increase the success rate of trabeculectomy in eyes that have undergone previous ocular surgery. Although antifibrotic agents have increased the likelihood of IOP control following filtering surgery, they have also increased the risk of complications. The prevalence of bleb leaks, bleb-related infections, and bleb dysesthesia associated with a perilimbal filtering bleb suggests the need to consider alternatives. Tube shunts (or glaucoma drainage implants) offer an alternative to trabeculectomy in the surgical management of glaucoma, and these devices have been growing in popularity in recent years. Practice patterns vary in the surgical management of glaucoma in eyes with previous ocular surgery. In 1996, Chen and colleagues conducted an anonymous survey of members of the American Glaucoma Society (AGS) and Japanese Glaucoma Society (JGS) to evaluate use of antifibrotic agents and tube shunts. The survey presented ten clinical situations requiring glaucoma surgical intervention. The majority of respondents (59-83%) preferred trabeculectomy with MMC for the clinical scenarios involving prior ocular surgery, although many of those surveyed elected to use a tube shunt, trabeculectomy with 5-FU, or trabeculectomy without an antifibrotic agent. In 2002, Joshi and associates re-administered the same survey to members of the AGS. Respondents still favored trabeculectomy with MMC, but the percentage usage of tube shunts had significantly increased. The greatest practice pattern shift was observed in patients with previous cataract and glaucoma surgery. In particular, selection of tube shunts as the preferred surgical approach increased from 7% to 22% in eyes with prior trabeculectomy, and increased from 8% to 22% in eyes with prior extracapsular or intracapsular cataract extraction. The lack of consensus among glaucoma surgeons regarding the use of tube shunts or trabeculectomy with an antifibrotic agent in eyes that have had prior cataract or glaucoma surgery likely relates to the fact that available clinical data has not shown one surgical procedure to be superior to the other. Similar surgical results have been reported with both glaucoma procedures in eyes with aphakia/pseudophakia and failed filters when studied separately. Success rates have ranged from 50% to 88% for tube shunts, and 48% to 86% for filtering surgery with an antifibrotic agent in case series studying aphakic/pseudophakic eyes. Success rates have ranged from 44% to 88% for tube shunts, and 61% to 100% for 5-FU and MMC trabeculectomy in eyes with failed filters. Comparable rates of severe complications have also been reported with tube shunt surgery and trabeculectomy with an adjunctive antifibrotic agent. The Tube Versus Trabeculectomy (TVT) Study was designed to prospectively compare the safety and efficacy of nonvalved tube shunt surgery and trabeculectomy with MMC. Patients with uncontrolled glaucoma who had prior cataract extraction with intraocular lens implantation and/or failed filtering surgery were enrolled in this multicenter clinical trial and randomized to placement of a 350 Baerveldt glaucoma implant (Advanced Medical Optics, Irvine, CA) or trabeculectomy with MMC (0.4 mg/ml for 4 minutes). The goal of this investigator initiated trial is to provide information that will assist in surgical decision-making in similar patient groups.

Official Title
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Tube Versus Trabeculectomy (TVT) Study

Conditions
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Glaucoma

Intervention / Treatment
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* Procedure: Baerveldt implant
* Procedure: Trabeculectomy with mitomycin C


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age 18 to 85 years Intraocular pressure greater than or equal to 18 mm Hg and less than or equal to 40 mm Hg Previous trabeculectomy, cataract extraction with intraocular lens implantation, or both Exclusion Criteria: Unwilling or unable to give consent, unwilling to accept randomization, or unable to return for scheduled protocol visits Pregnant or nursing women No light perception vision Active iris neovascularization or active proliferative retinopathy Iridocorneal endothelial syndrome Epithelial or fibrous downgrowth Aphakia Vitreous in the anterior chamber for which a vitrectomy is anticipated Chronic or recurrent uveitis Severe posterior blepharitis Unwilling to discontinue contact lens use after surgery Previous cyclodestructive procedure, scleral buckling procedure, or presence of silicone oil Conjunctival scarring precluding a trabeculectomy superiorly Need for glaucoma surgery combined with other ocular procedures (eg cataract surgery, penetrating keratoplasty, or retinal surgery) or anticipated need for additional ocular surgery

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 85 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Trabeculectomy<br>Trabeculectomy with mitomycin C | Procedure: Trabeculectomy with mitomycin C<br>* Patients will be randomized to receive either a Trabeculectomy (guarded filtration surgery) with mitomycin C (0.4 mg/ml for 4 minutes) or a 350 mm^2 Baerveldt glaucoma implant<br>|
| Active Comparator: Implant<br>Baerveldt Implant | Procedure: Baerveldt implant<br>* Patients will be randomized to receive a 350 mm^2 Baerveldt glaucoma implant or a Trabeculectomy (guarded filtration surgery) with mitomycin C (0.4 mg/ml for 4 minutes)<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Intraocular Pressure | The data value from the Baseline visit and 5 year follow-up visit were combined. Specifically, values were calculated by subtracting the 5 Year Intraocular Pressure from the Baseline Intraocular Pressure. | Baseline to 5 years | 
| Rate of Complications | Complications associated with both surgical procedures | 5 years | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Visual Acuity | Visual acuity was measured by the total number of letters read (correctly) using a ETDRS eye chart | 5 years | 
| Reoperations for Glaucoma | Reoperations for glaucoma was defined as additional glaucoma surgery requiring a return to the operating room. | 5 years | 
| Need for Supplemental Medical Therapy | The number of supplemental glaucoma medications required in the Implant Group and Trabeculectomy Group at 5 years | 5 years | 
| Failure Rate | Failure was prospectively defined as IOP greater than 21 mm Hg or less than 20 percent reduction below baseline on 2 consecutive follow-up visits after 3 months, IOP less than or equal to 5 mm Hg on 2 consecutive follow-up visits after 3 months, re-operation for glaucoma, or loss of light perception vision. | 5 years | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Glaucoma, Trabeculectomy, Tube shunt surgery