The excimer laser removes anterior corneal tissue layer by layer to a predetermined depth. It is able to do this precisely and accurately by using ultraviolet light. Clinical studies are underway to assess the safety and therapeutic effectiveness of the VISX Twenty/Twenty Excimer Laser System in performing phototherapeutic keratectomy (PTK) on pathological conditions of the cornea, and photorefractive keratectomy (PRK) to treat high myopia. Electron microscopic, immunohistochemical and morphometric analyses of epithelial-stromal interactions in the cornea, are being used to study wound healing after excimer laser surgery.

Following excimer keratectomy, there is a relative delay in the reformation of corneal epithelial basement membrane and adhesion structures. We performed morphometric analyses of the reformation of the epithelial adhesion structures in human corneal tissue after excimer laser treatment. Immunohistochemical techniques will also be used for epithelial basement membrane adhesion structure localization.

Extracellular matrix remodelling may determine the visual outcome of patients undergoing excimer keratectomy. The aims of our research are to obtain information about the expression in corneal tissue of collagenases and their inhibitors following excimer wounds and to correlate their levels with stromal scarring and remodelling. An organ culture wound-healing system will be used to determine the effect of collagenases, their inhibitors, and their activators.

The processes of stromal scarring and subsequent clearing, clinically observed 1 to 6 months post-excimer keratectomy, may be related to the balance of proteins involved in matrix regulation. Quantitative analysis of stromal collagenases will be determined before, during, and after scar formation and clearing. This will be correlated with corneal light scattering and with newly-synthesized collagen. These experiments aimed at elucidating the role of collagenase production, activation, and inhibition in post-excimer corneal matrix remodelling will increase our understanding of corneal wound healing as well.