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WJ Dupps, C Roberts; Stromal Collagen Crosslinking and Experimental Suppression of Central Islands in Excimer Laser Keratectomy . Invest. Ophthalmol. Vis. Sci. 2002;43(13):147.
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Purpose: To investigate potential mechanisms of central island generation in broad-beam refractive surgery by assessing the effect of preoperative stromal collagen crosslinking on central island formation. Methods: A glutaraldehyde-based crosslinking reagent was applied preoperatively to the deepithelialized corneas of ten human donor globes to induce stromal collagen crosslinking. Same-donor controls were exposed only to solvent. All corneas underwent sham ablation followed by phototherapeutic keratectomy (5-mm diameter, ∼100-um depth). Finally, saline was used as a hypotonic stimulus in postoperative swelling experiments to confirm effective stromal crosslinking. Triplicate stromal thickness and curvature measurements were acquired with an Orbscan scanning-slit topography system (v. 2.10B) before and after each experimental phase. Central islands were measured by subtraction of vertical meridian pachometry maps and described in terms of amplitude, width and decentration. Results: Crosslinking was confirmed by the nearly complete suppression of stromal thickening in GTA-treated corneas during postoperative swelling experiments. Intraoperative thickness changes consistent with central island formation were detected in all non-crosslinked controls (amplitude = 15 ± 9 um (mean ± sd), width = 2.26 ± 0.37 mm and decentration = 0.07 ± 0.16 mm) and in only 50% of crosslinked corneas (amplitude = 1 ± 1 um, width = 0.77 ± 0.82 mm and decentration = 0.06 ± 0.09 mm). Sham ablations in crosslinked and control corneas did not produce central islands. Conclusion: Preoperative collagen crosslink induction significantly decreased the incidence, amplitude (p = .002) and diameter (p < .001) of central islands in a donor model of keratectomy without alteration of the ablation algorithm. Central island formation is highly dependent upon the biomechanical state of the corneal stroma, and a better understanding of the role of hydration and tissue biomechanics is important for future design of broad-beam photoablation algorithms. View OriginalDownload SlideView OriginalDownload Slide
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