Glaucoma Drainage Devices : Glaucoma Drainage Devices Group 10:
Richard Pace Submitted to Dr. Thomas Boland
Clemson University Glaucoma : Glaucoma Second leading cause of blindness in the world
Affects over 66.8 million people worldwide
Condition of the eye, where the ocular fluid pressure rises to a level that is above 22mmHg  Risk Factors : Risk Factors Mutagens
Substances known to cause cancer
High Blood Pressure
African descendents are three times more likely to develop glaucoma than Caucasians
Inuit descendents are forty times more likely to develop closed angle glaucoma than Caucasians Treatment Options  : Treatment Options  Laser Trabeculoplasty — A laser light is used to open the channels in the Trabecular meshwork
Trabeculotomy — A small instrument is inserted into the drainage canal to create an opening through the Trabecular meshwork
Trabeculectomy — An opening is made in the channels of the Trabelular meshwork by surgerySeton Insertion — If all other methods fail, an implant is inserted into the eye with a valve, that allows the pressure to be relieved Trabeculectomy : Trabeculectomy Most common surgery used to lower the IOP.
Hole is made in the eye.
Fluid flows out.
Conjunctiva is pulled back.
Incision is made in the sclera and part of the trabecular meshwork is removed.
Procedure done under local anesthesia.
Fluid collects under the conjunctiva where it reabsorbed. Purpose of Drainage Devices : Purpose of Drainage Devices Intended for use in patients who have exhausted all other treatment methods
Decrease IOP of the eye
Draws aqueous humor buildup caused by glaucoma through a drainage tube and away from eye History of Drainage Devices : History of Drainage Devices 1912: The first translimbal glaucoma drainage device is implanted by Zorab ; device used silk thread to drain fluid
1969: Molteno announced that a large surface area is needed to disperse the aqueous beneath the conjunctiva. To this extent, he inserted a short acrylic tube attached to a thin acrylic plate. Most of the operations failed after the first 3-6 months because of plate exposure, tube erosion, and scar formation.
1976: First Molteno implant was introduced consisting of a long silicone tube attached to a large end plate placed 9-10 mm posterior to the limbus . The implant, which offered no resistance to the outflow, often resulted in hypotony , flat ACs , and choroidal effusions.
1992: It was discovered that increasing the surface area of the end plate(s) results in lower IOPs .
Baerveldt shunt introduced by George Baerveldt
nonvalved silicone tube attached to a large silicone plate with a surface area of 250 mm 2 , 350 mm 2 , or 500 mm 2
1993: Ahmed glaucoma valve (AGV) introduced by Mateen Ahmed
1997: Introduction of the Helies drainage device which uses an artificial meshwork of PTFE fibers
1998: Glaucoma Drainage Devices have been implanted in 2,980 patients
2001: FDA approved the AquaFlow ™ Collagen Glaucoma Drainage Device as an alternative treatment for open-angle glaucoma Procedure : Procedure An incision is made in the conjunctiva and a pocket is created below the iris
The implant is placed between the conjunctiva and the sclera and attached to the sclera
The drainage tube is trimmed and inserted into the front chamber of the eye, just in below and parallel to the iris Classifications : Classifications Two main classifications of implants
Only drains fluid at a certain IOP
Valve opens and fluid is drained into a reservoir where it is absorbed by surrounding tissues
Rely on resistance formed by fibrous capsule or bleb
Bleb grows around the implant and creates a space for fluid to drain and be absorbed by surrounding tissue Materials : Materials Medical grade silicone
Low tissue response to implantation
Resistant to bacterial growth
Does not stain or corrode other materials
Complies with FDA, ISO, and Tripartite biocompatibility guidelines for medical products
High tensile strength (1500psi), good elongation (to 1250%) and flexibiliby
Stable at a temperature range of -75-500oC
Resists water, oxidizing chemicals, ammonia, and isopropyl alcohol Picture from: http://www.kkchemicalindustries.com Materials : Materials Polypropylene
High flexibility and dimensional stability
Poor abrasion resistance
High tensile and compression strength
Chemically resistant to most alkalis and acids, organic solvents, degreasing agents, and electrolytic attack
Degrades in presence of UV light Picture from: http://www.chemicals-technology.com Materials : Materials Polytetrafluoroethylene or PTFE
Chemically inert to most chemicals including nitric, sulfuric, and phosphoric acids
Highly crystalline and stable
Low wear resistance
Inflammation caused by PTFE wear particles Picture from: http://itech.dickinson.edu Molteno Implants : Molteno Implants Developed by Dr. Anthony Molteno in the 1960’s.
Increase the surface area of the plate portion.
Original device was made out of PMMA.
Consisted of a short tube attached to a large plate.
Susceptible to erosion. Picture from: http://user.it.uu.se/~jonasn/images/eye1.jpg Molteno Implants : Molteno Implants Originally placed adjacent to the limbus, intersection of cornea and sclera, and attached to the sclera.
Moved to a position a few millimeters away from limbus to allow for better drainage.
New design: made of a silicone tube attached to a polypropylene plate.
175mm2 and 230mm2
Double plate. A vicryl tie is often used to prevent hypotony.
The tie closes off the drainage tube, preventing an excessive amount of fluid flow.
Dissolve in 4-5 weeks Molteno Implants : Molteno Implants Case Study 1 Use in patient with Sturge-Weber syndrome.
Initial IOP was 32mmHg in right eye and 37 mmHg in left eye.
Normal is 10-20mmHg.
Molteno implant placed into both eyes; vicryl tie used.
IOP checked 15 years later.
Lowered IOP to 15mmHg in both eyes.
Needed no post-op treatment. Case Study 2 Young man suffered a trauma to his right eye.
Received a trabeculectomy initially.
Failed after 5 years.
Had an IOP of 45-50mmHg.
Received a double plate Molteno implant.
IOP lowered to 13-17mmHg.
Implant has remained stable after 22 years.
No post-op treatment. Baerveldt Shunt : Baerveldt Shunt Created by George Baerveldt in 1992
Abbott Medical Optics
Made of medical silicone
BG 102-350 Pars Plana
Relies on growth of bleb
Increased surface areas allow for better IOP control
Patented Bleb Control Mechanism
Fenestrations allow tissue to grow through them
Control size and height of bleb
Minimizes motility disturbances Pictures from: http://www.amo-inc.com Ahmed Glaucoma Valve : Ahmed Glaucoma Valve Created by Mateen Ahmed in 1993
New World Medical
Extra plate to provide increased drainage
Extra plate to provide increased drainage Picture from: www.glaucomatoday.com Picture from: www.ahmedvalve.com Case Study : Case Study Patients with Ahmed S2 Glaucoma Valve or Baerveldt 250 mm2 were selected
Devices were compared
Found that patients with Ahmed S2 had a higher IOP than those with Baerveldt 250mm2 and were also on more medication at the last follow up visit
Ahmed S2 also had a higher failure rate but the Baerveldt implant had more complications  :  Oculieve was created by Dr. Michael Wilcox of Aqueous Biomedical.
Lack of Reservoir
Should Eliminate Major complications of most implants
Medical Grade Silicone Oculieve  Problems : Problems Bleb fails after 2-4 years
Fibrous capsule gets too thick
Micromovement of implant on the scleral surface initiates the wound healing response
Build up of scar tissue increases capsule thickness
Interferes with eye motility
Prevents aqueous humor from filtering through
When IOP is too low
Usually occurs shortly after surgery because the bleb has not had time to form yet
Clogging of the tube with blood or tissue
Extrusion of the shunt
Results in removal of implant and reimplantation elsewhere Works Cited : Works Cited Wilcox, Micheal J.. Aqueous Biomedical: http://www.aqueousbio.com/
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