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Proceedings Paper

Changes in corneal collagen induced by holmium:YAG laser irradiation
Author(s): George T. Timberlake; Martin H. Reinke; Alvin Miller
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Paper Abstract

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.

Paper Details

Date Published: 7 May 1996
PDF: 8 pages
Proc. SPIE 2681, Laser-Tissue Interaction VII, (7 May 1996); doi: 10.1117/12.239595
Show Author Affiliations
George T. Timberlake, Univ. of Kansas Medical Ctr. (United States)
Martin H. Reinke, Massachusetts Eye and Ear Infirmary (United States)
Alvin Miller, Univ. of Kansas Medical Ctr. (United States)

Published in SPIE Proceedings Vol. 2681:
Laser-Tissue Interaction VII
Steven L. Jacques, Editor(s)

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