Growth factor expression in corneal wound healing after excimer laser keratectomy.

PURPOSE

To develop a rabbit model of reproducible corneal haze after excimer laser keratectomy and to characterize expression of transforming growth factor beta (TGFbeta) and basic fibroblast growth factor (bFGF) in rabbit corneas during haze formation.

METHODS

Seven rabbits underwent a 100 microm deep phototherapeutic keratectomy (PTK) in one eye and a 15-microm shallow PTK in the contralateral eye. Corneal haze was compared at 1-20 weeks after surgery. Subsequently, 16 rabbits underwent 100-microm PTK in one eye and 15-microm PTK in the contralateral eye. Four rabbits were killed at 1, 2, 3, and 4 weeks, respectively, after surgery. Immunohistochemistry was performed on the corneas to localize the expression of TGFbeta and bFGF. Control subjects were rabbits that underwent either epithelial debridement alone or no surgery.

RESULTS

A 100-microm PTK resulted in significantly more corneal haze than a 15-microm PTK at every postoperative examination (p < 0.05). Both TGFbeta and bFGF were expressed in the scars at 1-4 weeks after deep and shallow excimer ablations. bFGF was expressed in the keratocytes of both treated and control corneas. Minimal TGFbeta was detected in the keratocytes of the control corneas, whereas prominent TGFbeta expression was noted in the keratocyte-like cells adjacent to the postkeratectomy scars.

CONCLUSIONS

The 100-microm PTK ablation resulted in significantly more corneal scarring than the 15-microm PTK ablation. Even though there was no immunohistochemical difference in the pattern of TGFbeta and bFGF expression after deep and shallow ablations, there was an association between the expression of the growth factors and corneal scarring after excimer laser keratectomy.