Corneal Opacity after Repeated Photorefractive Keratectomy

ABSTRACT

To study the histopathologic effects and possible collagen fiber alterations in corneal opacification after repeated photorefractive keratectomy(PRK) in human. PRK had been performed five times for 2 and 2/3 years using excimer laser. One year and ten months after last PRK, partial penetrating keratoplasty was performed. The cornea was stained with PAS, Alcian blue, Masson`s trichrome, Congo red. Oil red. O and stained immunohistochemically for collagens type III, IV, VI, VII. It was observed under light microscope(LM) and transmission electron microscope(TEM). LM findings showed thickening of epithelial layers, proliferation of subepithelial fibroblasts and absence of Bowman`s membrane. By TEM, disarray of collagen lamellae and electron dense deposits to adjacent keratocyte were observed. Histochemically, positive staining in Alcian blue, while negative in others. In immunohistochemistry, positive staining for type IV and VI collagens were noted. Corneal opacity after repeated PRK is due to deposits of type IV and VI collagens and acidic mucoprotein in extracelluar matrix, which is positive in Alcian blue stain.