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J.C. Erie, C.B. Nau, J.W. McLaren, D.O. Hodge, W.M. Bourne; Long–Term Keratocyte Deficits in the Corneal Stroma After LASIK and PRK . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4355.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine changes in keratocyte density up to 5 years after LASIK and PRK. Methods: 17 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. In PRK patients, cell densities were determined in 5 stromal layers; 0% to 10% (anterior), 11% to 33%, 34% to 66%, 67% to 90%, and 91% to 100 % (posterior). In LASIK patients, cell densities were determined in the stromal flap, the anterior and posterior halves of the 100–µm–thick retroablation layer, and the posterior third of the stroma (the region of the stroma that was ablated was omitted from analysis). Differences between pre– and post–operative cell densities were determined by using generalized estimating equation models with Bonferroni correction for 4 comparisons. Results: Before PRK, mean keratocyte density in the anterior 10% of the stroma was 32,084 ± 5,870 cells/mm3 (± SD). Cell density in this region decreased after PRK by 39%, 42%, 45%, and 47% at 1, 2, 3, and 5 years respectively (P<0.001). At 5 years after PRK, cell density was decreased by 20–24% in the posterior two thirds of the stroma (P<0.03). Before LASIK, mean keratocyte density in the stromal flap was 30,104 ± 4,576 cells/mm3. Cell density in the stromal flap decreased after LASIK by 23% (P<0.002) at 1 year and 37% (P<0.001) at 5 years. Cell density in the anterior retroablation layer decreased after LASIK by 18% (P<0.001) at 1 year and 43% (P<0.001) at 5 years. At 5 years after LASIK, cell density was decreased by 19–22% (P<0.02) in the posterior third of the stroma. Conclusions: Keratocyte densities are decreased for up to 5 years in the anterior stroma after PRK and in the stromal flap and in the anterior retroablation layer after LASIK. A decrease in posterior stromal keratocyte density is first noted at 5 years after LASIK and PRK. We also consider several artifacts of confocal microscopy that might explain some of these differences.
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