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LJ Muller, A de Wolf, E Pels, WJ Rijneveld, M-J Tassignon; What Corneal Anatomy Tells Us about Refractive Surgery . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4229.
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Purpose: Correction for myopia by cutting (radial-keratotomy, RK; laser induced in situ keratomileusis, LASIK) or ablating (photorefractive keratectomy, PRK; LASIK) healthy human corneas does not lead to proper wound healing regarding collagen and sensitivity. Despite this problem refractive surgery is well appreciated and the number of treated patients is increasing. To get more insight into the anatomy of the cornea after refractive surgery, buttons obtained from the operating theatre were investigated. Methods: Corneal buttons of patients who underwent RK (n=7), PRK (n=5) and LASIK (n=1) were immediately fixed and processed for light and electron microscopy. Large central, mid and peripheral areas were analysed. Reconstructions of tangential sections above and below the interface of the LASIK-flap were made. Results: The epithelium grows into the RK-cut or below the LASIK-flap. Near the ingrowth of the flap the number of layers covering the surface decreases to 3 and at the site of ablation, also in the PRK corneas, the number of layers increases up to 9. Variation in epithelial thickness seems to be related to its ingrowth and to the amount of ablated stromal tissue. Deep in the RK-cut and below the LASIK flap, two apposing epithelial cell layers are present, of which the basal epithelial cells are innervated by corneal nerves. Both techniques lead to undulation of collagen fibers near the incision and within the flap. Furthermore, the flap contains the interwoven most anterior stroma as observed in earlier swelling experiments. Conclusion: Corneal anatomy can help us to understand the outcome of refractive surgery concerning 1) decreased sensitivities and 2) ectasia after LASIK. Nerves follow basal epithelial cells into deeper stromal layers (1) and undulations in collagen bundles suggest a considerable reduction in tensile strength (2) .
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