In our San Diego Lasik Institute, the first step of any laser corneal re-shaping procedure is accessing the stroma, or the main structural part of the cornea. The top laser is a clear skin layer, the epithelium. If you were to laser that epithelium, it would just grow back like any skin layer would. Therefore, you have to get under that layer to access the main “meat” part of the cornea, or the stromal bed. The epithelium can grow back, the stroma does not.
PRK: was the original procedure performed with a laser re-shaping, and is still used in certain cases today. In this procedure, the clear skin layer is removed, the laser re-shaping done, and it then takes several days for the clear skin layer to grow back. Because of the extra time to heal, and the additional discomfort PRK can cause, LASIK came into being.
LASIK: a procedure whereby a flap consisting of the epithelium and a thin layer of the upper stromal bed is created so the stromal bed can be accessed for laser re-shaping. This allows the epithelial layer to remain intact except at the edge of the flap, and allows for the stroma to re-attach to itself after laser re-shaping. Over the years, it has been shown that it is most advantageous to create a thinner flap, thereby leaving more tissue in the bed to maintain the structure of the stroma and the cornea. It is also important to have a consistently thick flap, within a range that is predictable and does not vary by a large amount. Whether a femtosecond laser is used or a mechanical microkeratome is used, the goal is to get a consistent, reliable flap to maximize safety.
A minimum amount of stromal bed tissue must be left after laser re-shaping to maintain the structural integrity of the cornea. Therefore a reliable flap of thinner thickness is most advantageous so that the more stromal tissue can be left in the bed to ensure structural stability.
LASEK: A procedure where the epithelium is removed in one sheet after weakening with alcohol, and replaced after laser re-shaping is done. Supplanted by the more sophisticated Epi-LASIK procedure at Motwani Lasik Institute.
Epi-LASIK: A procedure where a flap of ONLY the epithelial layer is made, thereby maximizing the stromal bed available. This is similar to the PRK and LASEK procedure, but creates a epithelial flap without use of chemicals. This flap is created with an automated device. This is a TRUE FLAPLESS PROCEDURE, as no irreplaceable stromal tissue is used to create the flap. This is used in special cases where it is a higher amount of stromal tissue is needed due to high prescription, where Epi-LASIK is deemed safer for the patient, or where the patient desires such a procedure. Dr. Motwani is the only surgeon in San Diego who has the equipment and performs this procedure.