The AVB Study: Prospective Study Comparing the Ahmed Valve and the Baerveldt Implant for Treating Refractory Glaucoma
|First Received Date ICMJE||July 15, 2009|
|Last Updated Date||August 18, 2013|
|Start Date ICMJE||July 2005|
|Estimated Primary Completion Date||April 2014 (final data collection date for primary outcome measure)|
|Current Primary Outcome Measures ICMJE
||Surgical Failure (composite measure) [ Time Frame: 5 years ] [ Designated as safety issue: Yes ]|
|Original Primary Outcome Measures ICMJE
|Change History||Complete list of historical versions of study NCT00940823 on ClinicalTrials.gov Archive Site|
|Current Secondary Outcome Measures ICMJE
|Original Secondary Outcome Measures ICMJE
||Non-glaucomatous ocular pathology and interventions [ Time Frame: 5 years ] [ Designated as safety issue: No ]|
|Current Other Outcome Measures ICMJE||Not Provided|
|Original Other Outcome Measures ICMJE||Not Provided|
|Brief Title ICMJE||The AVB Study: Prospective Study Comparing the Ahmed Valve and the Baerveldt Implant for Treating Refractory Glaucoma|
|Official Title ICMJE||The Ahmed Versus Baerveldt (AVB) Study: Prospective, Multicenter Trial Comparing the Ahmed-FP7 Valve With the Baerveldt-350 Implant in Treating Refractory Glaucoma|
The purpose of this study is to compare the safety and efficacy of the Ahmed valve and the Baerveldt implant in treating refractory glaucoma. Eligible patients will be recruited from multiple study centers and randomized to a glaucoma drainage device for implantation. They will be followed long-term based upon outcome measures including intraocular pressure, glaucoma medication use, visual acuity, complications of the surgery and further treatments required.
The use of a glaucoma drainage device (GDD) is indicated in cases of refractory glaucoma not responsive to conventional medication, laser and surgical therapy. Most of these patients are at high risk for surgical failure, with serious concomitant ocular and systemic diseases. GDD's are increasingly being used to obtain low target intraocular pressures (IOP) in patients who have failed antimetabolite trabeculectomy or have active neovascular glaucoma.
Since Molteno's original design, several drainage devices have become commercially available for implantation. Currently, the two most commonly used devices are the Ahmed Glaucoma Valve (AGV) (New World Medical, Inc., Rancho Cucamonga, CA), and the Baerveldt Glaucoma Device (BGD) (Advanced Medical Optics, Santa Ana, CA). The AGV, with a venture-based flow-restrictive valve is helpful in minimizing postoperative hypotony and complications associated with hypotony, including flat anterior chamber, choroidal effusions, and suprachoroidal hemorrhage. However, there appears to be a high rate of encapsulation and hypertension associated with this device, and increased requirement of postoperative glaucoma medication use. The BGD, a non-valved device, requires early ligature of flow by the use of a suture restriction to allow adequate time for bleb formation. Although this can result in an initial post-operative hypertension phase, it results in less encapsulation and theoretically fewer postoperative glaucoma medications and better IOP control. However, the lack of a flow-restrictor and the large filtering surface area may result in a greater risk for hypotony related complications.
Although several studies comparing the AGV and BGD have been reported, they have all been retrospective, nonrandomized, small scale, and compare different patient populations. The results have been inconclusive and conflicting in evaluating the relative efficacy and characteristics of these two devices, and further research needs to be done in order to answer these questions.
The Ahmed vs. Baerveldt (AVB) Study is the first multicenter prospective randomized clinical trial comparing the Ahmed FP7 valve and the Baerveldt-350 tube shunt glaucoma drainage devices. Primary outcome is surgical failure, a composite criteria evaluating the intraocular pressure lowering effect of the devices, complications of the surgery, treatments for complications, glaucoma medication use, and the preservation of visual acuity. Secondary outcomes will evaluate these variables individually, and any non-glaucoma related ocular pathology and required interventions.
AVB Study Manual:
An AVB Study Manual including the study design and protocol, standardized surgical technique, patient education and consent form, and data collection protocol was distributed to each clinical site. The contents of the manual received ethics approval by the Institutional Review Board (IRB) at the primary site.
Patient Enrollment and Treatment Assignment:
Patients were recruited from 7 study sites by 10 surgeons. After patient eligibility and written informed consent was obtained by the Site PI, randomization to placement of an Ahmed FP7 valve or a Baerveldt-350 tube shunt was made by coin toss.
Pre-operative data collection:
The following data was collected in the 3 months prior to surgery: date of birth, gender, race, glaucoma diagnosis and etiology, past ocular history (diagnoses, surgical and laser procedures), best corrected visual acuity, intraocular pressure, glaucoma medication use, abnormal slit lamp findings, and abnormal fundus exam findings.
The surgical procedures used for the AVB Study are standardized, and any complications during surgery will be noted and defined.
Ahmed FP7 valve implantation:
A superior or inferior corneal traction suture with 8-0 Vicryl was placed for globe fixation as required. A 90-degree conjunctival peritomy was followed by blunt dissection to mobilize a fornix or limbus-based conjunctival flap over the area of intended device implantation. Non-preserved lidocaine 1% was injected under the conjunctival flap, posteriorly, and under the extraocular muscle bellies with a blunt cannula. Gentle cautery was used to obtain hemostasis.
The Ahmed Glaucoma Valve model FP-7 was primed with balanced salt solution, and placed in the intended quadrant. The plate was sutured to sclera 8-10mm posterior to the limbus with two 8-0 or 10-0 Nylon sutures.
A paracentesis was made if required, and a viscoelastic agent used to form the anterior chamber. A 22-gauge needle was used to create needle tract into the anterior chamber.
The tube was trimmed, and placed into the anterior chamber through the needle tract. The tube was attached to the sclera using a 10-0 Nylon suture if required. A sclera or corneal graft was placed over the tube and sutured to the sclera with 10-0 Nylon.
The conjunctival flap was closed with 8-0 or 10-0 Vicryl suture. At the conclusion of the case, Maxitrol ointment was placed on the eye. No patients were patched, although shields were given to patients. That day, patients were started on antibiotic and steroid eye drops. A cycloplegic was used as indicated.
Baerveldt-350 tube shunt implantation:
A superior or inferior corneal traction suture with 8-0 Vicryl was placed for globe fixation. A 90 to 120-degree conjunctival peritomy was followed by blunt dissection to mobilize a fornix or limbus-based conjunctival flap over the area of intended device implantation. Non-preserved lidocaine 1% was injected under the conjunctival flap, posteriorly, and under the extraocular muscle bellies with a blunt cannula. Gentle cautery was used to obtain hemostasis.
Both adjacent extraocular muscles were isolated using a muscle hook. 4-0 silk sutures were used for fixation if necessary.
The Baerveldt drainage device model BG101-350 was checked with balanced salt solution, and a 4-0 Nylon releasable intraluminal suture was placed. A 7-0 or 8-0 Vicryl ligature suture was placed around the tube. The plate was placed in the intended quadrant and under the muscle bellies. The plate was sutured to the sclera 8-12mm posterior to the limbus with two 8-0 or 10-0 Nylon sutures.
A paracentesis was made if it was required, and a viscoelastic agent used to form the anterior chamber. A 22-gauge needle was used to create needle tract into the anterior chamber. The tube was trimmed, and placed into the anterior chamber through the needle tract. The tube was attached to the sclera using a 10-0 Nylon suture if required. A sclera or corneal graft was placed over the tube and sutured to the sclera.
The conjunctival flap was closed with an 8-0 or 10-0 Vicryl suture. At the conclusion of the case, Atropine 1% drops and Maxitrol ointment was placed on the eye. No patients were patched, although shields were given to patients. On the day of surgery, patients were started on antibiotics and steroid eye drops. A cycloplegic agent was used as indicated.
Post-operative data collection:
Patients were seen post-operatively at a minimum of 1 day, 1 week, 2 weeks, 1 month, 2 months, 3 months, 6 months, 12 months, 18 months 2 years, 3 years, 4 years and 5 years. Further visits were made as deemed necessary. At each visit, the following data was collected:
Based upon the pre-operative data and post-operative results, a study outcome will be assigned to each patient, as defined below:
Complete Success: (requires all of the following criteria)
Qualified Success: (requires all of the following criteria)
Failure: (if any of the following criteria are met)
|Study Type ICMJE||Interventional|
|Study Phase||Phase 3|
|Study Design ICMJE||Allocation: Randomized
Endpoint Classification: Safety/Efficacy Study
Intervention Model: Parallel Assignment
Masking: Open Label
Primary Purpose: Treatment
|Study Arm (s)||
* Includes publications given by the data provider as well as publications identified by ClinicalTrials.gov Identifier (NCT Number) in Medline.
|Recruitment Status ICMJE||Active, not recruiting|
|Estimated Completion Date||April 2014|
|Estimated Primary Completion Date||April 2014 (final data collection date for primary outcome measure)|
|Eligibility Criteria ICMJE||
|Ages||18 Years and older|
|Accepts Healthy Volunteers||No|
|Contacts ICMJE||Contact information is only displayed when the study is recruiting subjects|
|Location Countries ICMJE||Chile, Canada, United States|
|NCT Number ICMJE||NCT00940823|
|Other Study ID Numbers ICMJE||CVEC-AVB, GRSC-2005|
|Has Data Monitoring Committee||No|
|Responsible Party||Panos G. Christakis, Credit Valley EyeCare|
|Study Sponsor ICMJE||Credit Valley EyeCare|
|Collaborators ICMJE||Glaucoma Research Society of Canada|
|Information Provided By||Credit Valley EyeCare|
|Verification Date||August 2013|
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