Quantitative assessment of corneal wound healing following intralasik using in vivo confocal microscopy

Purpose: To compare the response of the cornea to laser in situ keratomileusis (LASIK) with flap creation using the IntraLase FS15, FS30, and FS60 femtosecond lasers. Methods: A retrospective analysis of 55 patients (55 eyes) who underwent LASIK with flap creation using IntraLase was performed. Twelve FS15 patients (12 eyes), 14 FS30 patients (14 eyes), and 29 FS60 patients (29 eyes) were examined 3 months postoperatively by in vivo confocal microscopy. The accuracy of flap thickness, number of interface particles, interface backscatter, epithelial thickness, and activation of keratocytes were determined from the confocal data. Results: Keratocyte activation was detected in 14 of 55 eyes. In general, keratocyte activation was limited to 1 or 2 cell layers adjacent to the interface. However, 2 eyes exhibited multiple layers of activation by confocal microscopy as well as significant clinical haze by slit-lamp examination. Keratocyte activation and interface backscatter were positively correlated with the raster energy used during surgery (R = 0.51, P < .01) and increased when the steroid treatment time was reduced. Overall, the difference between actual and intended flap thickness was 11.2 ± 8.6 μm, and the density of interface particles was 19.9 ± 12.1 particles/mm². Conclusions: LASIK with IntraLase provides more reproducible flap thickness and fewer interface particles than previously observed with use of mechanical microkeratomes. However, IntraLase can induce more significant keratocyte activation, which may underlie clinical observations of haze and transient light sensitivity syndrome in some patients. Activation can be avoided by using lower raster energies and an extended steroid treatment regimen.