Corneal response to laser intrastromal keratomileusis

Purpose. Keratomileusis in situ combined with excimer laser which is performed in the bed underneath a superficial flap (LAS IK) is a procedure now available in refractive surgery that requires the use of a microkeratome Its major advantage is to avoid haziness after excimer laser surgery A histopathological study is performed to evaluate the stromal response in cases of LASIK Methods. Three patients with keratoconus were submitted to LASIK procedures before keratoplasty The cornea! buttons were obtained eight days, five months and one year aftei the LASIK The three corneas were processed for light and transmission electron microscopy (TEM) Results CASE I (eight daysA An epithelial ingrowth represented by a row of epithelial cells is observed The cut is well defined with increase in the number of keratocytes There is an inflammatory reaction composed of lymphocytes, plasma cdls, neovessels and multinucleated giant cells engulfing foreign body material. CASE.' (five months) A very mild loss of keratocytes is observed, being the cut surface smooth and regular, with no damage of the adjacent tissue. CASE 3 (one year) The normal epithelium had grown over the defect created by the microkeratome An epithelium face' has been left at one edge of the flap A fold of the Bowman's layer was observed at the other end of the flap The TEM showed close apposition of the flap, mild disorganization of the fibers and presence of keratocytes nuclei embedded in an extracellular matrix Conclusion, The mechanism of corneal healing involved in the LASIK procedure includes reorganization of the epithelium, mild inflammation which disappears over time and proliferation of fibroblasts The absence of stromal deoosits after LASIK mav be responsible for the lack of haziness.