Keratocyte Density in the Human Cornea After Photorefractive Keratectomy

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Abstract
Objective To perform a quantitative analysis of keratocyte density in human corneas after photorefractive keratectomy (PRK). Methods In a prospective comparative trial, 24 eyes of 14 patients received PRK to correct refractive errors of between –1.25 diopters (D) and –5.75 D. Corneas were examined by using confocal microscopy before and 1 day, 5 days, and 1, 3, 6, 12, 24, and 36 months after PRK. Keratocyte nuclei were counted in 5 stromal layers in 3 to 6 scans per eye per visit. Keratocyte density in each layer post-PRK was compared with the density in the corresponding layer of the pre-PRK full stroma (included stroma that would later be photoablated) and the pre-PRK future unablated stroma (thickness adjusted by omitting the future ablation depth) (Bonferroni-adjusted paired t test). Results Keratocyte density in the anterior 10% of the post-PRK stroma decreased by 25% (P = .002), 41% (P<.001), 40% (P<.001), 43% (P<.001), and 45% (P<.001) at 3, 6, 12, 24, and 36 months compared with the anterior 10% of the pre-PRK full stroma and was reduced by 15% at 36 months (P = .02) compared with the anterior 10% of the pre-PRK future unablated stroma. Conclusion After PRK, keratocyte density in the anterior stroma is not restored to the high-density levels found in the preoperative stroma.