STUDIES ON THE MECHANISM OF HAZE FORMATION AFTER PHOTOREFRACTIVE KERATECTOMY / 解剖学报

ABSTRACT

Objective To study the mechanism of haze formation after photorefractive keratectomy (PRK). Methods 27 adult New Zealand white rabbits were employed in this study.24 of them received PRK in the right eye and laser in situ keratomileusis (LASIK) in the left eye at the same time and under the same condition for -10^00D ablation at once,24hour,1 week,2 week,1month,3 month,6 month and 12 month after surgery,the corneas were examined periodically by slip\|lamp microscopy for haze formation,and the both eyes of 3 rabbits were enucleated,the corneas were studies with light microscopy;transmission electron microscopy;immunohistochemical evaluation for extracellular matrix,including collagen type Ⅰ,type Ⅲ,type Ⅵ,cellular fibronection,tenascin and laminin;RT\|PCR detection for mRAN of collagen type Ⅰ. Results The incidence of haze was 100% after PRK.No haze formation after LASIK.Haze was located at the anterior stroma immediately adjacent to the ablated areas.The change of structure and composition which correlated with haze formation was due to a combination of the following factorsthe basement membrane of corneal epithelium was discontinuous;A new layer of subepithelium tissue was synthesized;fibroblast was increased in number and activated;the collagen fibrils were disorganized.The diameter of fibrils and the space between the fibrils were irregular in the anterior stroma;The newly synthesized extracellular matrix inculding collagen type Ⅰ,type Ⅲ,type Ⅵ,cellular fibronection,tenascin and laminin were deposited in the anterior corneal stroma.Conclusion\ The formation and disappearing of haze was the result of interreaction between fibroblast and extracellular matrix.The destruction of basement membrane of corneal epithelium and Bowmen's member after PRK is initializing factor during haze formation.\;[