Relation between corneal haze and transforming growth factor-beta 1 after photorefractive keratectomy and laser in situ keratomileusis

Purpose: To investigate the relation between corneal haze formation and tra nsforming growth factor-beta (TGF-beta) after photorefractive keratectomy ( PRK) and laser in situ keratomileusis (LASIK). Setting. Department of Ophthalmology, University of Tokyo Graduate School o f Medicine, Tokyo,Japan. Methods. White rabbits were divided into 4 groups, with each group receivin g 1 of the following surgeries: manual epithelial abrasion, PRK, lamellar k eratotomy, or LASIK, The degree of corneal haze was quantitatively analyzed by measuring the light scattering intensity of corneas before and 4 and 12 weeks after surgery. The expression of type IV collagen and TGF-beta1 in t he corneas at baseline and at 4 weeks was examined immunohistochemically. Results: The light scattering intensity was significantly greater 4 and 10 weeks after PRK. In contrast, epithelial abrasion, lamellar keratotomy, and LASIK did not influence the light scattering intensity of the corneas. Typ e IV collagen was detected in the basal lamina of the corneal epithelium an d in Descement's membrane in the normal cornea. After epithelial abrasion, there was no change in the distribution of type IV collagen, Four weeks aft er PRK the expression of type IV collagen was detected in the subepithelial layer of the laser-ablated area. Four weeks after lamellar keratotomy, typ e IV collagen was linearly and fragmentarily detected in the corneal stroma . Four weeks after LASIK, type IV collagen was linearly and continuously de tected in the corneal stroma and was detected slightly in the subepithelial region of the laser-ablated area. In the normal corneas, the expression of TGF-beta1 was not detected in the keratocytes. Four weeks after PRK, the e xpression of TGF-beta1 increased in the keratocytes that proliferated in th e subepithelial fibrous layer. In contrast, epithelial abrasion, lamellar k eratotomy, and LASIK did not change the expression pattern of TGF-beta1 in the keratocytes. Conclusion: The multiplier effect of epithelial abrasion and excimer laser ablation in PRK may increase the expression of TGF-beta1 in keratocytes and induce corneal haze. (C) 2001 ASCRS and ESCRS.