Purpose:
To measure changes in keratocyte density seven years after laserin situ keratomileusis (LASIK) and photorefractive keratectomy(PRK).
Methods:
Sixteen eyes of 11 subjects received LASIK and 18 eyes of 12subjects received PRK to correct myopia or myopic astigmatism.Corneas were examined by confocal microscopy before and at 6months, 1, 3, 5, and 7 years after surgery. A custom automatedprogram objectively identified bright objects (presumed to bekeratocyte nuclei) in confocal images and calculated keratocytedensity in anterior to posterior stromal layers. Differencesbetween preoperative and postoperative cell densities were comparedby using paired t-tests with Bonferroni correction for fivecomparisons. Minimum detectable differences (MDD, α=0.01, ß=0.20)were calculated for non-significant differences.
Results:
After LASIK, keratocyte density decreased to 71%, 68%, and 83%of preoperative density in the anterior flap, posterior flap,and anterior retro-ablation zone, respectively, by 1 year andthereafter remained decreased through 7 years. After PRK, keratocytedensity decreased to 74% of preoperative density in the anterior10% of the stroma by 1 year and thereafter remained decreasedthrough 7 years.
Conclusions:
Keratocyte density remains decreased in the anterior stromathrough seven years after LASIK or PRK. The effect of long-termkeratocyte deficits is unknown.Keratocyte Density after LASIK(mean ± SD [MDD])KeratocyteDensity after PRK (mean ± SD [MDD])
Keywords: cornea: stroma and keratocytes • refractive surgery • microscopy: confocal/tunneling