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7 May 1996 Changes in corneal collagen induced by holmium:YAG laser irradiation
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Holmium:YAG laser thermokeratoplasty corrects hyperopia (farsightedness) by producing small areas of corneal collagen shrinkage that cause the central cornea to bulge outward, increasing optical power. Collagen shrinkage is probably caused by laser-heated corneal water, but details of the shrinkage mechanism are not known. We investigated the shrinkage mechanism by measuring changes in corneal ultrastructure, surface shrinkage, water content, and strength following Ho:YAG laser exposures. Morphological changes in collagen were documented by measurements from electron micrographs. Corneal adhesive strength was determined by measuring tearing force in a plane parallel to the corneal surface. Laser-induced water loss was measured by weighing corneal samples before and after exposure. Corneal surface shrinkage was assessed by photographing the movement of particles on the cornea. Lasered collagen fibrils increased in diameter, lost their orderly arrangement, and appeared `frayed.' The corneal surface contracted toward lasered areas with a maximal shift of approximately 190 micrometers , more than could be explained by a model based on collagen fibril changes. Water loss plays a minor role in corneal shrinkage since corneal samples lost about only about 1.4% of their weight after massive laser exposure. Despite marked changes in collagen structure, corneal adhesive force was unchanged.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
George T. Timberlake, Martin H. Reinke, and Alvin Miller "Changes in corneal collagen induced by holmium:YAG laser irradiation", Proc. SPIE 2681, Laser-Tissue Interaction VII, (7 May 1996);

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