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E.J. Winter, J.C. Erie, C.B. Nau, J.W. McLaren, D.O. Hodge, W.M. Bourne; Recovery of Corneal Subbasal Nerve Density Is Slower After LASIK Than After PRK . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4371.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To measure corneal reinnervation during 5 years after LASIK and PRK. Methods: 16 eyes of 11 patients received LASIK with a planned 180–µm flap to correct refractive errors between –2D and –11D. 18 eyes of 12 patients received PRK to correct refractive errors between –1.5D and –5.75D. Corneas were examined by using confocal microscopy before and at 1, 2, 3, and 5 years after the procedures. Subbasal nerves and their branches were traced and their lengths measured by using a custom program. Nerve density was expressed as length of nerve per unit area (µm/mm2). Differences between pre–and post–operative nerve densities were determined by using generalized estimating equation models (to account for possible correlation between paired eyes) with Bonferroni correction for 4 comparisons. Results: Mean subbasal nerve density before PRK was 6786 ± 1948 µm/mm2 (±SD). Mean density decreased to 2764 ± 1321 µm/mm2 (–59%, P<0.001) at 1 year. At 2 and 5 years, mean nerve density returned to 6242 ± 1763 µm/mm2 (–8%) and 5903 ± 3086 µm/mm2 (–13%) respectively, densities not significantly different from densities before PRK (P=1.0). Mean subbasal nerve density before LASIK was 5589 ± 2436 µm/mm2. Mean density was 2745 ± 2913 µm/mm2 (–51%, P=0.001) at 1 year, 3661 ± 2773 µm/mm2 (–35%, P=0.03) at 2 years, and 3683 ± 2517 µm/mm2 (–34%, P=0.006) at 3 years. By 5 years after LASIK, density recovered to 4441 ± 2819 µm/mm2 (–21%, P=0.58). Conclusions: After LASIK, nerve fiber bundles return to the subbasal layer more slowly than they do after PRK.
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