Objective: To compare the effects of epipolis laser in situ keratomileusis (Epi-LASIK) and laser-assisted subepithelial keratectomy (LASEK) on the corneal stromal cells, and to evaluate their effects on corneal haze histopathologically.
Methods: Forty-eight New Zealand white rabbits (96 eyes) were randomly treated with Epi-LASIK in one eye and LASEK in the other, and 2 rabbits (4 eyes) without any treatment were used as control. Cornea stromal cell apoptosis was evaluated by terminal deoxyribonucleotidyl transferase-mediated deoxynuridine triphosphate nick end labeling (TUNEL) assay. Stromal cells proliferation and myofibroblasts generation were evaluated by immunocytochemical analyses the expression of Ki-67 and alpha-smooth muscle actin (alpha-SMA) respectively. Myofibroblast generation was further testified by Western blot analysis of alpha-SMA. Both number of TUNEL, Ki-67 and alpha-SMA positive cells and expression of alpha-SMA were semi quantitatively analyzed to explore their effects on corneal haze.
Results: Many TUNEL-positive cells appeared in the central anterior stromal in early stages after both LASEK and Epi-LASIK, and the number of TUNEL-positive cells reached a peak 24 hours after either LASEK or Epi-LASIK. There were more TUNEL positive cells found in LASEK group than that in Epi-LASIK group in 1 week postoperatively (t = 3.63, 7.80, 4.34, 2.95, all P < 0.01). There were a lot of Ki-67-positive cells in anterior corneal stroma after both LASEK and Epi-LASIK, but the peak appeared at 72 hours after the treatments. The significant difference was also found in the number of Ki-67-positive cell between the two treatments in 1 week postoperatively (t = 3.81, 5.85, 5.09, 5.59, all P < 0.01). alpha-SMA-positive cells started to appear apparently at 1 week after both LASEK and Epi-LASIK, and both the peaks appeared at 1 month after the treatments, and there were still a lot of alpha-SMA-positive cells in corneal stroma at 3 months after LASEK. There were more alpha-SMA-positive cells found after 1 week in LASEK group than that in Epi-LASIK group (t = 2.97, 7.19, 6.73, all P < 0.01).
Conclusion: There are less stromal cell apoptosis, proliferation and myofibroblast generation in Epi-LASIK than that in LASEK. Therefore, comparing with LASEK, Epi-LASIK induces less corneal haze response in correcting myopia.