The LASEK is a technique derived from the PKR, which divides the main time; with the difference that the epithelium before pelé (after application of a diluted alcohol solution) is repositioned on the surface of the cornea after issuance of the laser beam. LASEK is a technique called surface (absence of stromal flap cutting)
LASEK: technique and principle
This variant of the PKR was proposed there are a dozen years to reduce pain and transient inflammation observed after contact as the PKR techniques. The main difference with the PKR is that unlike this one, off epithelium from the underlying corneal stroma is rested after issuance of the treatment by the excimer laser. The idea was to allow a faster healing, cell epithelial re applied immediately covering the area receiving the laser. It was also expected a reduction of the risk of "haze". The haze is a partial opacification of the fabric corneal stromal, related to the presence of inflammatory organelle in cells of the cornea (keratocytes), and the acquisition by these cells contractile properties, reducing the regularity of the extra-cellular matrix (and thus its transparency). The biological casecade at the origin of these cellular changes being initiated by the interactions between the epithelium in the division and the keratocytes, the rest of the epithelium was supposed cut the time of contact between dividing cells and corneal stroma. Well-conducted clinical studies have not confirmed this benefit.
This technique requires the surgeon to take off this corneal epithelium carefully, trying to form a continuous sheet. The application of alcohol diluted to 20 ° for 20 seconds easy detachment of the epithelium: ethanol dissolves the structures allowing the basal cells of the epithelial sheet to join the corneal stroma.
The benefits induced by the repositioning of the epithelial sheet is not clearly demonstrated, both in terms of operating comfort, and prevention of complications as the haze. This disappointment was made on account of the toxic effect of alcohol on epithelial cells. Today, LASEK is a technique abandoned in favor of the PKR (where the epithelium is not réapposé after photoablation). However, the technique of desepithelialisation to alcohol can be used to take off quickly and Atraumatic way corneal epithelial sheet.