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Li Chen, Anatoly Fabrikant, Ling C. Huang, Arlene Gwon, Dimitri A. Chernyak; Morphological Changes due to Wound Healing in Rabbit Cornea. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1493.
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Mathematical models of corneal wound healing following refractive surgery have previously been described by a low-pass spatial filter due to flap-based draping effect as well as the epithelial remodeling. Here we investigated the postoperative corneal morphological changes induced by various iFS-assisted ablation patterns in a rabbit model.
8 eyes from 4 New Zealand black rabbits were used for this pilot study. An IntraLase iFS laser system was used to perform the designed corneal cuts with flaps on 4 rabbit corneas and without flaps on the other 4 rabbit corneas, respectively. Simple geometrical patterns, such as center cut or ring cut with different depths and diameters, were conducted on the corneas with or without flaps. Preoperative (preop) measurements were made by slit lamp biomicroscopy, wavefront aberrometry, and corneal topography to establish the baseline. The postoperative (postop) measurements up to 2-month were also performed on each surgical eye. Corneal histopathology at 2-month was used to validate the designed cuts. Evaluations of corneal changes were compared with the preop, 1-week postop, and 2-month postop corneal topography measurements including 2D pachymetry and Scheimpflug images.
Wavefront measurements were conducted successfully on all preop rabbit eyes with a 6mm pupil, but not on the postop eyes due to the strong curvature changes at the transition zones. Corneal pachymetry showed an overall decrease in corneal thickness that was fairly stable in the 4 eyes with flaps and had greater variability in the 4 eyes without flaps. In the 4 eyes that underwent the designed cuts without flaps, the average thinnest corneal thickness at 1-week postop was 257±43μm which was similar to the designed thickness 256±16μm; while the average thinnest corneal thickness at 2-month postop was 328±40μm which was 72 micron thicker than the designed thickness. In the 4 eyes that underwent the designed cuts after a 100μm depth flap, the average thinnest corneal thickness at 1-week postop was 271±34μm which was similar to the designed thickness 269±44μm, while the average thinnest corneal thickness at 2-month postop was 36μm thicker than the designed thickness. Scheimpflug images and corneal topography profiles from the postop measurements show corneal smoothing process both on corneal cuts with and without flap during the corneal wound healing.
This study demonstrated considerable postoperative morphological changes in corneal wound healing following corneal surgery in rabbit eyes. The result is important for the design of customized ablation algorithms to correct existing preoperative aberrations while avoiding the generation of new aberrations, such as spherical aberration.
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