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D Borja, F Manns, V Fernandez, P Lamar, P Soederberg, W Smiddy, W Smiddy, J-M Parel; Temperature-Induced Corneal and Scleral Shrinkage Using a Thermoelectrically-Controlled Device . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4123.
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Purpose:To determine the kinetics of thermal shrinkage in corneal and scleral strips. Methods:A thermoelectrically-controlled device was constructed to induce thermal shrinkage in corneal and scleral strips of eye-bank eyes. The device consists of a copper cuvette filled with Dextran solution that holds the corneal or scleral strip; a thermoelectric cell controlled by a temperature controller designed to increase the temperature of the cuvette up to 90oC; an inductive displacement sensor that measures the change in length of the heated tissue; a loading system that places the tissue strip under a load calculated to simulate intraocular pressure. The thermoelectric shrinkage device was calibrated and preliminary shrinkage experiments were conducted on corneal and scleral strips from 8 eye-bank eyes that were cut into 2x4mm rectangular strips. One end of the strip was glued into the cuvette using cynoacrylate glue and the other end was attached to the loading system. The temperature inside the tissue strip was measured with a thermocouple. The initial and final tissue temperature was set at 33oC. Corneal and scleral shrinkage induced when the temperature was increase to 75oC for 5 minutes was recorded. Results:The time constant of the temperature increase in the cuvette from 33oC to 75oC was approximately 9s. The measured shrinkage curves fit a second-order kinetic model. In all experiments, shrinkage started when the temperature reached approximately 65oC. The exponential time constant for shrinkage was approximately 30 s and maximum shrinkage after 5 minutes ranged from 60 to 70%. Conclusion:The thermoelectric shrinkage device produces controllable and repeatable shrinkage in corneal and scleral tissue strips. Our preliminary results seem to confirm that thermal shrinkage of the cornea and sclera is a second-order kinetic process. Supported in part by the Whitaker Foundation; Henri and Flore Lesieur Foundation; Florida Lions Eye Bank; and Research to Prevent Blindness, New York, NY.
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