Primary Tube Versus Trabeculectomy Study

• Intraocular pressure [ Time Frame: 1 day, 1 week, 1 month, 3 months, 6 months, 1 year, 18 months, 2 years, 3 years, 4 years, 5 years ] [ Designated as safety issue: No ]
  

• Complication rates [ Time Frame: 1 day, 1 week, 1 month, 3 months, 6 months, 1 year, 18 months, 2 years, 3 years, 4 years, 5 years ] [ Designated as safety issue: Yes ]
  
• Visual acuity [ Time Frame: 1 day, 1 week, 1 month, 3 months, 6 months, 1 year, 18 months, 2 years, 3 years, 4 years, 5 years ] [ Designated as safety issue: Yes ]
  
• Visual field [ Time Frame: 1 year, 2 years, 3 years, 4 years, 5 years ] [ Designated as safety issue: Yes ]
  
• Reoperation for glaucoma [ Time Frame: 1 day, 1 week, 1 month, 3 months, 6 months, 1 year, 18 months, 2 years, 3 years, 4 years, 5 years ] [ Designated as safety issue: No ]
  
• Supplemental medical therapy [ Time Frame: 1 day, 1 week, 1 month, 3 months, 6 months, 1 year, 18 months, 2 years, 3 years, 4 years, 5 years ] [ Designated as safety issue: No ]
  

Glaucoma surgery is indicated when further intraocular pressure (IOP) lowering is needed despite the use of maximum tolerated medical therapy and appropriate laser treatment. Trabeculectomy (or guarded filtration procedure) is the most frequently performed glaucoma opertion. Eyes with previous ocular surgery and certain secondary glaucomas (e.g. neovascular glaucoma and uveitic glaucoma) are at greater risk of trabeculectomy failure. Wound healing modulation with antifibrotic agents, like mitomycin C (MMC) and 5-fluorouracil (5-FU), has been shown to increase the success of glaucoma filtering surgery in high risk eyes. The use of MMC and 5-FU has become widespread in clinical practice. The improved efficacy of trabeculectomy with an adjunctive antifibrotic agent in high risk eyes has prompted their use in eyes considered to be at low risk for failure. A randomized clinical trial found similar IOP reduction and surgical complications with the intraoperative application of MMC and 5-FU in eyes undergoing primary trabeculectomy.

Although antifibrotic agents have increased the likelihood of IOP control following glaucoma filtering surgery, they have also increased the risk of complications. The prevalence of bleb-related infections, bleb leaks, and bleb dysesthesia associated with a perilimbal filtering bleb suggests the need to consider alternative surgical approaches. Favorable results have been reported with tube shunts (or glaucoma drainage implants), and these devices have been growing in popularity. In particular, the large surface area of the Baerveldt glaucoma implant combined with its ease of insertion in a single quadrant offers an advantage over other tube shunts. Similar surgical results have been reported with tube shunts and trabeculectomy with MMC or 5-FU when studied separately in similar patient groups. A comparable rate of serious complications has also been reported for the Baerveldt implant and trabeculectomy with an antifibrotic agent in a retrospective study.

The Tube Versus Trabeculectomy (TVT) Study is a multicenter randomized clinical trial comparing the safety and efficacy of tube shunt surgery using the Baerveldt glaucoma implant and trabeculectomy with MMC in 212 patients with previous ocular surgery. Tube shunt surgery was more likely to maintain IOP control and avoid persistent hypotony or reoperation for glaucoma than trabeculectomy with MMC during the first year of follow-up in the TVT Study. Tube shunt surgery and trabeculectomy with MMC produced similar IOP reduction at 1 year, but there was less need for supplemental medical therapy following trabeculectomy. There were a large number of surgical complications during the first year of follow-up in the TVT Study, but most were transient and self-limited. The incidence of postoperative complications was higher following trabeculectomy with MMC than tube shunt surgery. However, severe complications resulting in reoperation and/or vision loss occurred with similar frequency with both surgical procedures. Vision loss occurred at a similar rate following tube shunt surgery and trabeculectomy with MMC. Patients who experienced surgical complications had greater vision loss than patients without complications.

The results of the TVT Study suggest the need to compare the safety and efficacy of tube shunt surgery and trabeculectomy with MMC in patients at low risk of surgical failure, including eyes without previous ocular surgery. The Primary Tube Versus Trabeculectomy (PTVT) Study is a multicenter randomized clinical trial that is similar in design to the TVT Study. Enrolled patients are randomized to undergo placement of a 350mm2 Baerveldt glaucoma implant or trabeculectomy with MMC. Baseline characteristics of the study population will be tabulated for each treatment group. Outcome discrimination between the two treatment groups will include IOP, surgical complications, visual acuity, visual fields, glaucoma reoperation, and need for supplemental medical therapy. Data will be collected at the normal postoperative visits at 1 day, 1 week, 1 month, 3 months, 6 months, 1 year, 18 months, 2 years, 3 years, 4 years, and 5 years after surgery.