Why is there a flap in Lasik Eye Surgery?

Refractive surgery has evolved greatly over several decades. Surgery to correct nearsightedness first took root and began to flourish as Radial Keratotomy (RK) during the 1970s and 1980s in the United States. This surgery required full thickness cuts with a diamond blade through the cornea. As technology developed, eventually the excimer laser was developed and the era of LASIK eye surgery was born.

Today, Laser refractive surgery has reached its pinnacle in LASIK (Laser Assisted in-situ Keratomileusis). Lasik has been termed the “flap-and-zap” surgery because it requires the creation of a flap of corneal tissue. This flap is gently lifted out of the way and the Excimer laser “zaps” the remaining cornea to reshape it and eliminate the patient’s nearsightedness, farsightedness, or astigmatism.


LASIK eye surgery

Although, LASIK eye surgery has now become the most common refractive eye surgery, many people do not understand why the flap is so important and how it came into practice.

Originally, laser refractive surgery came into being as PRK (Photorefractive Keratectomy). PRK is simply LASIK without a flap.

To perform PRK, the outer cellular layer (epithelium) of the cornea is stripped off of the eye by mechanical or laser scraping, or by use of alcohol. Over the course of a few days after the procedure, this epithelium grows back to provide a protective layer and a smooth optical surface.

LASIK was developed in order to avoid stripping off the epithelium by creating a flap of surface tissue that is lifted out of the way and then replaced after the laser reshaping. Although it adds an additional surgical step, it provides significantly faster healing, less pain, and a much speedier recovery of vision for the patient.

The original tool to create the flap is called a microkeratome and was used for many years in a surgery called Automated Lamellar Keratoplasty (ALK). In ALK surgery, the microkeratome was used to create a tissue flap and then a second microkeratome cut was made to remove corneal tissue to eliminate nearsightedness.

The microkeratome uses a high speed vibrating razor blade and plates of varying thickness to make cuts in the cornea. The concept was very similar to LASIK except that there was no laser involved. In ALK, a mechanical microkeratome was used both to create the flap and also to make a “refractive cut”, thus altering the optics of the eye.

The marriage of the ALK flap making microkeratome with the PRK laser technology is what gave genesis to LASIK eye surgery. ALK lacked the precision for the optics that could only be achieved with a laser. By uniting the flap technology and the laser technology, we were able to have surgical outcomes that were both relatively precise as well as fast healing.

Most recently, we have been able to do away with the mechanical microkeratomes entirely. The development of the femtosecond lasers like the Intalase FS Laser™ allowed us to have the same laser precision and safety for the creation of the LASIK flap as well as for the laser optical correction.


“Flap and zap” LASIK eye surgery

The same logic that lead surgeons to abandon the ALK technology for the excimer laser also lead us to abandon the ALK technology for flap creation once the laser technology was fully developed. Today, we are able to perform a “flap-and-zap” technique which is fully laser based without the imprecise mechanical razor bladed microkeratomes of old.

This pinnacle of technology allows us to treat with a level of confidence and precision that was never dreamed of in the ALK era and could never be accomplished using that old style equipment. The benefits of LASIK eye surgery to our patients are impressive. The all Laser era has truly delivered a faster healing, more precise, and safer refractive eye surgery.


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