Tube Versus Trabeculectomy (TVT) Study
Condition: Glaucoma
MeSH terms: Glaucoma
Study type: Interventional

Summary: 
      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: 
      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.
    

Intervention name(s): Baerveldt implant; Trabeculectomy with mitomycin C
Intervention type(s): Procedure; Procedure
Intervention description(s): 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); 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
Intervention MeSH terms: Mitomycins; Mitomycin
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Glaucoma; Trabeculectomy; Tube shunt surgery