EVects of amniotic membrane on epithelial wound healing and stromal remodelling after excimer laser keratectomy in rabbit cornea

Aims—To investigate if the amniotic membrane (AM) promotes epithelial migration while inhibiting stromal remodelling associated with corneal haze after excimer laser keratectomy. Methods—A wound 150 μm in depth and 6.0 mm in diameter was produced in 40 rabbits using an excimer laser. One eye was randomly chosen to be covered by the AM while the other eye served as a control. Epithelial wound healing was evaluated, together with any morphological changes of the anterior stroma connected with corneal haze. These morphological changes were histopathologically analysed using dichlortriazinyl aminofluorescein (DTAF), Masson trichrome staining, and an image analyser. Results—The AM group had a short latent phase followed by fast epithelial healing (p<0.001) during the early wound healing period and a significant decrease in the inflammatory response, together with a smaller change in the number of keratocytes than the control group. The mean thickness of the regenerated stroma was significantly thinner in the AM group than in the control group at 8 weeks (p<0.0001). The AM group had a more regular architecture of regenerated stromal lamella at 8 weeks and significantly less haze after 4 weeks than the control group (p<0.05). Conclusion—Use of the AM as a dressing on a corneal wound created by excimer laser surgery, in which severe haze is expected, may induce rapid epithelial healing with less inflammatory response. The AM may inhibit the irregular synthesis of stromal collagen that is associated with corneal haze. (Br J Ophthalmol 2001;85:345–349) The excimer laser has been used for the correction of myopic refractive error (photorefractive keratectomy, PRK) and for the treatment of superficial corneal opacification and surface irregularities (phototherapeutic keratectomy, PTK). Although both technical and clinical advances have been made in the application of excimer lasers to the cornea, the scattering of light that follows regeneration of the corneal stromal tissue can interrupt visual improvement after surgery. The severity of corneal haze is thought to be influenced by the amount of attempted correction, especially in patients undergoing deep stromal photoablation, and may be related to the amount of regenerated stroma. To reduce corneal haze following photoablation, attempts have been made to simulate the wound healing process. Topical steroids were found to inhibit haze 9 while the presence of the epithelium ensured rapid wound healing with minimal tissue proliferation. The repopulated stromal keratocytes after a corneal wound subsequently synthesise collagen and extracellular matrix during stromal remodelling, both of which may be associated with the development of corneal haze and a change in clinical refraction. 11–13 The ideal result of corneal wound healing following photoablation would therefore be rapid reconstruction of the corneal epithelium with minimal stromal re-