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J.D. Javier, J.B. Lee, D.T. Azar; Effect of the Epithelial Flap on Scar and Collagen Formation after Laser Subepithelial Keratomileusis (LASEK) on Leghorn Chick Eyes . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1428.
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Purpose:To evaluate the effect of the epithelial flap on scar and collagen formation after laser subepithelial keratomileusis (LASEK) and compare it to photorefractive keratectomy (PRK) in the Leghorn chick corneal model. Methods: LASEK surgery was performed on leghorn chick corneas and the morphologic changes were examined by confocal microscopy and transmission electron microscopy (TEM). Leghorn chick corneal epithelium was debrided mechanically with a blade or was exposed to 20% ethanol for 30 seconds and then treated with an excimer laser. The epithelial flap, epithelial basement membrane, and stroma was evaluated by indirect immunoflourescence using laminin, collagen III, and dichlorotriazinylaminofluorescein (DTAF) and TEM at 1, 2, 3, 7, 14, and 28 days post surgery. Epithelial sheet viability was demonstrated by culturing an epithelial sheet after exposure to 20% ethanol for 30 seconds. Results: Fragmented fluoresceince–positivity to laminin was detected beneath the epithelial flap during the immediate postoperative period and at day 1, increasing in intensity post LASEK. Laminin could only be observed from day 2 after PRK. There was more collagen III and neo stromal tissue demonstrated in the PRK group compared to the LASEK group at 1 month after the surgery. Tissue cultures of the harvested epithelial sheets survived and flourished 5 days after surgery. Conclusions:Less subepithelial stromal tissue and scarring was observed in LASEK treated eyes compared to the PRK treated eyes in the leghorn chick model. Early postoperative relative preservation of epithelial basement membrane and survival of epithelial cells might reduce epithelial–keratocyte interactions which can induce stromal scarring post excimer laser treatment.
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