Epi-LASIK, PRK, and LASEK all differ from LASIK in that no LASIK flap is created – they are surface procedures. Otherwise, epi-LASIK, PRK, and LASEK are essentially identical to LASIK. Dr. Shapiro finds the results of epi-LASIK, PRK, and LASEK to be the same as LASIK, but the recovery time of these procedures is longer than seen with LASIK. Epi-LASIK, PRK, and LASEK 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.
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 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 it underlying cornea, Dr. Shapiro carefully slides the epithelial sheet of tissue to the side of the cornea. After the wavefront guided laser is applied to the cornea, a spatula like instrument is used to reposition the epithelial sheet back over the cornea and a bandage contact lens is applied to the cornea to protect the epithelial layer.
Epi-LASIK is very similar to LASEK, except that no alcohol solution is used to swell the ultra-thin epithelial skin layer off of the surface of the cornea. Instead, the epithelial skin layer is removed by an oscillating blunt instrument called the “epi-keratome.” As with LASEK, the epithelial skin layer is folded off to the side of the cornea and the wavefront guided laser sculpture is applied. As with LASEK, the epithelial skin sheet is then repositioned over the cornea and a bandage contact lens is applied to protect the flap.
While LASEK and epi-LASIK are very similar, there are pros and cons to each one. With LASEK, the exposure of the underlying corneal surface may be more perfect than with epi-LASIK, but LASEK may be harder on the epithelial sheet in many cases than epi-LASIK, in which no dilute alcohol is used.