We plan to evaluate the application of alloplastic materials as potential substitutes for donor corneal lenticles in the correction of aphakic refractive errors. We will study high, medium, and low water content hydrogel lenticles preground by the manufacturers in the dry state to assume wet state parameters similar to donor corneal keratophakia lenticles. All studies will be performed in a previously established baboon model. Six months postoperatively following documentation of refractive shifts, we will subsequently remove and/or exchange they hydrophilic lenticles. This would be an analogous situation to those cases of pediatric aphakia whose lenticle power would need to be reduced as the eye grows. Refractive error shifts will be documented by digitization of corneascope photographs. Correlative microscopy will be used to analyze the morphologic features of each procedure. We next plan to evaluate refractive surgical procedures that correct as astigmatism and myopia. We will create an astigmatism model using a suture induced or wound disparity technique in a monkey. The induced astigmatism will subsequently be corrected with an oval or trapezoid shaped keratotomy produced with a diamond knife or by toric intracorneal implants made of donor baboon cornea or preground hydrophilic lenticles. We plan to correct myopia by implanting hydrogels designed to flatten the anterior corneal curvature or by producing controlled, central stromectomies in a monkey model. We finally plan to improve predictability of the procedures by analysis of corneal topographic shifts following refractive surgical procedures by establishing pattern recognition of corneascope photographs before and after experimental and clinical procedures and by developing improved computer formulae based upon analysis of experimental and clinical specimens. The use of preground, standardized donor materials could potentially be applied in the correction of pediatric aphakia. An improved understanding of the effects of keratotomy incisions on the correction of astigmatism can be applied to cases of high and irregular post cataract or post corneal transplant astigmatism. The ability to flatten the cornea in a unilateral high myope could potentially be utilized to prevent amblyopia.
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