Development of No-Rejection Aqueous Humor Pressure Control Membrane in The Eyeball for Glaucoma Implant Devices
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DEVELOPMENT OF NO-REJECTION AQUEOUS HUMOR PRESSURE CONTROL MEMBRANE IN THE EYEBALL FOR GLAUCOMA IMPLANT DEVICES Y. Sato, J.M. Parel* and M. Murahara The Faculty of Engineering, Tokai University 1117 Kitakaname Hiratsuka Kanagawa 259-1292, Japan *Bascom Palmer Eye Institute, University of Miami 900 N.W.17th Street, P.O. Box 016880, Miami, Florida33101 ABSTRACT The inner porous part of the PTFE [poly-tetrafluoroethylene] membrane was substituted with a hydrophilic group using irradiation by an ArF laser. Water was employed for a defluorination agent in order to inhibit rejection. The membrane was developed that automatically pumps out water when the pressure is raised above a fixed value. The increased intraocular pressure with aqueous outflow failure causes glaucoma. In healthy humans intraocular pressure is maintained at a normal physiological level of between 8 to 18 mmHg. When the pressure exceeds 21 mmHg, a diagnostic of glaucoma may be predicted. We designed a new type of membrane to pump the aqueous humor and regulate its outflow. The membrane has gained characteristics of aqueous humor penetration by substituting a part of a hydrophobic group that exists inside the porous PTFE with the hydrophilic group. Furthermore our previous studies have found that B, Al and H atoms are effective for defluorination of atoms from fluorocarbon. In this study three kinds of reaction liquid containing B, Al and H respectively were used. By this defluorination reaction B and Al atoms were better than H atoms. We prepared a boric acid water solution (B(OH)3), nitro aluminate water solution (Al(NO3)3) and water (H2O) as chemical compounds for defluorination and OH substitution. When ethyl alcohol is dropped on the porous PTFE, it penetrates into inner porous PTFE easily. When the three kinds of chemical compound water solutions are dropped onto the porous PTFE membrane, the solution is trapped up to the inner side of porous PTFE. When each sample with hydrophilic property treatment was implanted into rabbits’ eyes and its biocompatibility was tested, some samples using Al and B atoms for defluorination have shown the rejection reaction called neoplasm blood vessel. However, the other samples using water as the reaction liquid have shown no rejection. INTRODUCTION Glaucoma due to hindrance of aqueous circulation is caused by intraocular pressures exceeding 20 mmHg. As the result, a retinal nerve fiber is disordered. And when the pressure exceeds 22 mmHg, humans may lose sight usually requiring an operation before blindness occurs. Filtering surgery is clinically applied as a method of operation, however results of these operations are extremely diverse. Therefore decompression methods using devices implanted into the eye were proposed. Presently the clinically applied devices are the Molteno implant [1,4] Almed Glaucoma valve [2] made of polypropylene, and the Baerverlt glaucoma valve [3] made of silicon tube. These devices are effective for decompression a short term after implantation. However the intraocular pressure cannot be
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