Both LASEK and PRK differ from LASIK in that no LASIK flap is created. Otherwise, both LASEK and PRK are essentially identical to LASIK. Dr. Shapiro finds the results of both LASEK and PRK to be the same as LASIK, but the recovery time of these procedures is longer than with LASIK. LASEK and PRK are used in cases in which it is not safe or not optimal to create a LASIK flap, such as a cornea which is either too thin or too biomechanically weak to support a LASIK flap.
The cornea is covered by an ultra-thin, clear skin layer called the “epithelial layer.” This microscopically thin layer is only 5 cells thick – about half the thickness of a human hair. This ultra-thin tissue is one of the fastest healing tissues in the human body.
PRK
When PRK is performed, the ultra-thin skin layer is removed, the excimer laser is used to reshape the underlying cornea, and the skin layer is allowed to grow back . The quality of the optics will be determined by the quality of the laser sculpture. Dr. Shapiro prefers using customized wavefront guided laser sculpture to give the most optimal optical results. After the laser sculpting is performed, in the case of PRK, the ulta-thin epithelial layer is allowed to grow back, which typically takes approximately four days. To protect the healing skin layer, a very thin, highly breathable contact lens, called a “bandage contact lens,” is placed on the cornea. It is called a “bandage contact lens” because it acts like a Band Aid. Dr. Shapiro places the bandage contact lens on the eye immediately following PRK and Dr. Shapiro removes the lens about a week later. Typically, patients cannot tell the lens is in place.
LASEK
LASEK is a modification of PRK. It differs from PRK only in how the ultra-thin epithelial skin layer is handled. In the case of PRK, the epithelial layer is removed and allowed to grow back over the cornea. In the case of LASEK, on the other hand, the epithelial skin layer is repositioned back into place to cover the cornea.
With LASEK, the epithelial layer is first loosened by the application of a painless, ultra-dilute alcohol solution to the surface of the cornea. This causes the ultra-thin epithelial layer to swell off the underlying cornea. Once the epithelial layer has swelled off the underlying cornea, Dr. Shapiro carefully slides the epithelial sheet of tissue to the side of the cornea. The wavefront guided excimer laser is then used to sculpt in the exact same vision correcting shape as it does for wavefront guided LASIK or wavefront guided PRK (in fact, all these procedures differ only in how the eye is prepared before the laser is applied). Once the precise wavefront guided laser sculpting is done to correct the optics of the eye, the epithelial sheet (which is sometimes called an “epithelial flap” –analogous to the more sustentative LASIK flap) is carefully reposition back to cover the lasered area. This is different from PRK in which this epithelial tissue is removed and allowed to grow back. A bandage contact lens is placed over the eye for one week, as with PRK. The repositioned epithelial sheet (“epithelial flap”) covers the cornea during the healing phase as new corneal cells migrate centrally to replace the cells in the epithelial “flap.”
The original hope with LASEK was that it would reduce recovery times from those seen with PRK. Typically, with PRK, the patient experiences four days of burning, tearing, and light sensitivity after surgery – typically most notably on the second and third day. By the fourth day, full comfort is typically restored. However, Dr. Shapiro, and many other refractive specialists, feels that the recovery with LASEK is not statistically different from that seen with PRK.
Dr. Shapiro prefers a hybrid technique that uses elements of both classical PRK and LASEK techniques.