Corneal stromal changes after LASIK

PURPOSE: To assess stromal modifications after laser in situ keratomileusis (LASIK) for myopia using in vivo confocal microscopy. METHODS: Thirteen eyes from 10 patients were examined before surgery and at days 8 and 30 after surgery using an in vivo confocal microscope coupled with a Z-Scan system. Stromal morphological changes, keratocyte density, flap thickness, and subclinical haze were evaluated and compared at different time points. RESULTS: Microfolds at the Bowman's layer were found in 55%, eyes as well as variable reflectivity particles located at the interface level in all postoperative examined eyes. The mean flap and activated-cell area thicknesses were respectively, 101+/-28 micrometer and 50.5+/-14 micrometer with a significant negative correlation (r=-0.89, p=0.01). The intensity of the added peak (47.3+/-8.6% scattered light), corresponding to the subclinical haze, as measured by Z-Scan, was also negatively correlated with the flap thickness (r=-0.89, p=0.01). CONCLUSION: This study confirms the presence of microfolds and particles at the interface level as subclinical complications. Evaluating the keratocytic activation by confocal microscopy can lead to a better understanding of corneal wound healing after LASIK and can help to improve the techniques. The flap thickness seems to be involved in the cellular activation induced by LASIK.