Earlier Intraocular Pressure Control After Ahmed Glaucoma Valve Implantation for Glaucoma
Condition: Glaucoma
MeSH terms: Glaucoma
Study type: Interventional
Phase: Phase 4

Summary: 
      The purpose of this study is to compare the occurrence rate of the high pressure phase and
      the final pressure outcomes between patients treated with glaucoma medication prior to the
      expected onset of the high pressure phase to those patients who have glaucoma medication
      started at the onset of the high pressure phase. The investigators hypothesize that if
      glaucoma medications are started prior to the expected onset of high pressure phase, the high
      pressure phase will not occur as frequently and the ultimate pressure level will be lower
      than if the glaucoma medications are started at the onset of this phase.
    

Detailed description: 
      Tube shunt procedures are a popular surgery for the control of glaucoma. Tube shunt devices
      are designed to drain eye fluid (aqueous humor) through a tube inserted into the front
      chamber of the eye (anterior chamber) to a plate secured to the mid-posterior section of the
      outer eyeball wall. The body then lays down collagen tissue and forms a capsule around the
      plate. The fluid filters through the capsule of collagen tissue and is reabsorbed into the
      ocular and systemic circulation. The collagen tissue continues to remodel itself over a long
      period of time (up to years). However, a well characterized, yet poorly understood,
      phenomenon occurs in many patients in the 4-8 weeks after the device's implantation, called
      the hypertensive phase. The pressure of the eye can increase from a desirable level of about
      10 immediately after the tube shunt implantation to much higher levels, in the range of 20 to
      30's, and then it may gradually return to less than 20. Such a high pressure phase can cause
      irreversible damage an eye with glaucoma. The usual management of a high pressure phase is to
      start glaucoma medications as soon as it is detected. A previous study we conducted showed
      that this high pressure phase resolves in about half of patients with medical therapy, but
      the other half may continue to have higher than expected pressures. The exact cause of this
      high pressure phase is unknown. However, it is postulated that the mechanism may involve a
      compaction collagen tissue layers under the eye's own fluid pressure while the collagen
      tissue is being laid down, which in turn creates a firm, dense capsule that makes escape of
      fluid difficult. Therefore, it is argued that if the formation of eye fluid is reduced by
      medication during this initial period when the collagen tissue is laid down, the compaction
      of collagen, and subsequently the high pressure phase may be avoided.

      The purpose of this study is to compare the occurrence rate of the high pressure phase and
      the final pressure outcomes between patients treated with glaucoma medication prior to the
      expected onset of the high pressure phase to those patients who have glaucoma medication
      started at the onset of the high pressure phase. We hypothesize that if glaucoma medications
      are started prior to the expected onset of high pressure phase, the high pressure phase will
      not occur as frequently and the ultimate pressure level will be lower than if the glaucoma
      medications are started at the onset of this phase.

      We believe that this study will have a very significant impact on the management of glaucoma
      with tube shut procedures. If it is true that the rate and pressure level of the hypertensive
      phase can be reduced by simply starting glaucoma medications to reduce the formation of eye
      fluid before the expected the high pressure phase begins, which is generally 4 weeks after
      implantation of the tube shunt device, glaucoma patients can be saved from exposure to the
      very high level of eye pressure, and the eventual pressure control may be better.
    

Intervention name(s): glaucoma medications (Timolol, Brimonidine, Dorzolamide, Brinzolamide)
Intervention type(s): Drug
Intervention description(s): Subjects may receive glaucoma medications after Ahmed valve implantation
Other intervention name(s): Timolol, Brimonidine, Dorzolamide, Brinzolamide
Intervention MeSH terms: Timolol; Brimonidine Tartrate; Dorzolamide; Brinzolamide
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Glaucoma tube shunt procedure