Purpose: To determine changes in keratocyte density up to 3 years after LASIK.
Design: Prospective, nonrandomized, comparative trial.
Participants: Seventeen eyes of 11 patients received LASIK with a planned 180-microm flap to correct refractive errors between -2.0 diopters (D) and -11.0 D (mean, -6.56+/-2.44).
Methods: Corneas were examined by using confocal microscopy before LASIK and 1, 3, 6, 12, 24, and 36 months after LASIK. Bright objects that resembled keratocyte nuclei were manually counted by a masked observer. Cell densities were determined in anterior and posterior halves of the stromal flap, anterior and posterior halves of the 100-microm-thick layer immediately behind the ablation (retroablation layer), and the posterior third of the stroma. The region of stroma that was ablated (as measured 1 month after LASIK) was omitted from preoperative analysis. Cell densities after LASIK were compared (using1-factor repeated-measures analysis of variance) with densities in the corresponding layer of the normal preoperative stroma (which served as its own control).
Main outcome measure: Corneal keratocyte density.
Results: Before LASIK, keratocyte densities in the anterior and posterior stromal flap and the anterior retroablation layer were 34 818+/-5108 cells/mm(3) (mean +/- SD), 25 390+/-4045 cells/mm(3), and 21 328+/-2980 cells/mm(3), respectively, and densities in these layers decreased 14% to 20% at 1 month after LASIK (P<0.001). Keratocyte densities in these layers remained stable at 3 and 6 months, and then gradually decreased further (P<0.001) to 26% to 36% below pre-LASIK densities by 3 years. Keratocyte densities in the remaining stromal layers did not change after LASIK.
Conclusion: Keratocyte densities in the stromal flap and in the anterior retroablation layer decrease during the first 6 months after LASIK and then decrease further during the next 2.5 years. Further studies on these patients and others are warranted to confirm these findings and learn their significance.