Laser epithelial keratomileusis (LASEK) is only used on certain groups of patients, for instance when LASIK treatment is not possible because the cornea is too thin.
This method does not create a classic flap; rather, the top layer of the cornea (epithelium) is detached with alcohol (LASEK) and rolled up (see Figure 1). The surgeon then uses the excimer laser to model the shape of the corneal layers beneath (see Figure 2). To close the wound, the previously removed surface layer of cells is placed back and protected with a therapeutic contact lens. The corneal epithelium grows on in approximately 5 days. More postoperative complaints (delayed wound healing or even scarring) may occur with LASEK than with LASIK. The limit of -6 dpt for short-sightedness, +3 dpt for long-sightedness and 3 dpt for corneal astigmatism should not therefore be exceeded with LASEK.
Figure 1
Figure 2
Photorefractive keratectomy (PRK) is the predecessor of LASEK and LASIK. Contrary to those two methods, the surface layer of cells that was removed is not placed back after lasering, rather a soft contact lens is placed over the wound as a bandage. Within several days the epithelium grows back from the edge of the cornea. With this process, however, there are more postoperative complaints such as pain, fluctuating visual acuity and haze formation. In addition, vision improves more slowly than with other methods. PRK is therefore now rarely used.
The most recent development is to use a dull planer to prepare the epithelial flap like the wing of a door which is folded back again after laser correction. This procedure, known as Epi-LASIK, should also not be used beyond -6 dpt.
The PRK method can also be used as a special therapy for removing surface scars or pathological changes in the cornea. In that case, the method is known as phototherapeutic keratectomy (PTK).
