Comparison of stromal remodeling and keratocyte response after corneal incision and photorefractive keratectomy.

PURPOSE We investigated the keratocyte response and stromal remodeling after corneal incision and photorefractive keratectomy to understand the histophysiological and immunohistochemical differences between these two types of surgery. METHODS Corneal incision or photorefractive keratectomy was performed in rabbits or rats. Then we chronologically observed the histological changes and the changes in the localization of extracellular matrix proteins. RESULTS In both types of surgery, the keratocyte population at the damaged stroma became sparse, and the cells began undergoing apoptosis immediately after the surgical procedure. Subsequently, activated keratocytes migrated into the acellular zone, and the cells formed multiple layers at the resurfaced subepithelial regions. We observed deposition of amorphous substances between keratocytes that had migrated, and stromal remodeling appeared to start. Three months after surgery, the corneal structure had recovered to a near-normal condition at the corneal incision. After photorefractive keratectomy, however, extracellular matrix proteins were strongly immunoreactive at the subepithelial regions. CONCLUSIONS These results suggest that the stromal wound-healing processes are similar after corneal incision and photorefractive keratectomy. A corneal incision may induce a transient keratocyte response during stromal remodeling, but photorefractive keratectomy may induce a sustained keratocyte response.