Earlier Intraocular Pressure Control After Ahmed Glaucoma Valve Implantation for Glaucoma

Study Overview
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Brief Summary
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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
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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.

Official Title
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Earlier Intraocular Pressure Control After Ahmed Glaucoma Valve Implantation for Glaucoma

Conditions
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Glaucoma

Intervention / Treatment
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* Drug: glaucoma medications (Timolol, Brimonidine, Dorzolamide, Brinzolamide)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients requiring Ahmed glaucoma valve implantation to control intraocular pressure between the ages of 18 and 85 years. Exclusion Criteria: Unwilling or unable to give consent or unwilling to accept randomization. Patient out of area and potentially unavailable for follow-up visits. Known allergic reaction to timolol, brimonidine, dorzolamide, brinzolamide, or sulfa drugs. Known medical contraindications to the use of beta-blockers, including congestive heart failure, heart block, asthma, and chronic obstructive pulmonary disease. Concurrent intraocular procedure with Ahmed glaucoma valve implantation Previous Ahmed glaucoma valve implantation

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 |
| --- | --- |
| Experimental: Research arm (postop IOP>10)<br>Receive glaucoma medications if the eye pressure more than 10 mmHg after AHmed valve implantation | Drug: glaucoma medications (Timolol, Brimonidine, Dorzolamide, Brinzolamide)<br>* Subjects may receive glaucoma medications after Ahmed valve implantation<br>* Other names: Timolol, Brimonidine, Dorzolamide, Brinzolamide;|
| Active Comparator: Standard of care arm (postop IOP>17)<br>Receive glaucoma medication if eye pressure more than 17 mmHg after Ahmed valve implantation | Drug: glaucoma medications (Timolol, Brimonidine, Dorzolamide, Brinzolamide)<br>* Subjects may receive glaucoma medications after Ahmed valve implantation<br>* Other names: Timolol, Brimonidine, Dorzolamide, Brinzolamide;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Rate of Hypertensive Phase After Ahmed Valve Implantation for Glaucoma | Intraocular pressure more than 21 mmHg during the first 6 months after Ahmed valve implantation after the pressure has been reduced to less than 22 mmHg in the first postoperative week | within 6 months after surgery | 
| Intraocular Pressure Control After Ahmed Valve Implantation for Glaucoma | intraocular pressure comparison between groups after the Ahmed valve implantation | 3 weeks after surgery | 
| Intraocular Pressure of Eyes With Hypertensive Phase Versus Without Hypertensive Phase | intraocular pressure of eyes with hypertensive phase versus without hypertensive phase | 1 year after surgery | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Glaucoma tube shunt procedure