PURPOSE
The aim of the study was to compare corneal wound healing after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) using conventional, immuno- and enzymohistologic methods.
METHODS
Sixteen white Russian rabbits in each group underwent PRK or LASIK. Keratocyte density was recorded from 1 week to 6 months post-operatively on conventional histological sections. Immunohistologic cellular fibronectin and tenascin were used as markers of early epithelial and stromal wound healing in the cornea. The cell damage was demonstrated enzymohistologically using alkaline phosphatase.
RESULTS
The reaction was similar in quality with both methods and occurred at sites of simultaneous epithelial and stromal injury. Mild scarring was found around the edge of the flap after LASIK; PRK-treated corneas developed a central subepithelial haze and scarring. A hypocellular region was found in the anterior part of the ablation zone shortly after PRK. Fibroblast migration later led to hypercellularity and subsequent clinical haze formation. After LASIK this reaction was limited to the peripheral entry point of the microkeratome blade around the edge of the corneal flap, where cellular fibronectin and tenascin reactions were positive. An acellular zone was found anterior to the interface after LASIK. The keratocyte damage visualized by alkaline phosphatase was more extensive after PRK than after LASIK.
CONCLUSION
The stromal reaction to surgery was more extensive after PRK than after LASIK. A cytokine-mediated interaction between the epithelium and stroma was suggested as the cause of keratocyte cell migration and scar formation.