LASIK surgery and a similar procedure called PRK are used to correct vision in a non-diseased eye so that in many cases the patient no longer needs to wear glasses or contact lenses. First introduced in the U.S. in the 1990s, the already safe procedures continue to become safer and more accurate, and the recovery time has also been cut down.
LASIK surgery is basically a two-step procedure in which a flap is cut into the upper layer of the cornea that allows the surgeon to use a laser to vaporize tissue from the inner cornea to correct the vision. PRK, a procedure that pre-dated LASIK, is performed on the surface of the cornea with an excimer laser, and recovery from surgery takes four days.
The next development in this type of procedure was the introduction of a mechanical instrument called the microkeratome to make a small flap of the outer cornea, which cut recovery time to one day. Within the past five years, the femtosecond laser has been commonly used to make the flap, which has made the procedure more precise so that it provides better results, notes Gary Markowitz, M.D., of Delaware Eye Care Center. As with the microkeratome laser, recovery takes just a day.
In PRK surgery, no flap is cut into the cornea. Instead, the central portion of the thin outer layer of the cornea is loosened with a dilute alcohol solution and removed from the eye, which allows the laser to be applied to the surface of the cornea to correct the vision. Because there is no cutting, PRK eliminates even the slightest chance of the flap coming off that exists with LASIK, says Bruce Sumlin, M.D., of Halpern Ophthalmology Associates. That’s why PRK is the procedure of choice for those whose cornea is too thin for LASIK. The flap-less procedure of PRK is also well-suited to those whose jobs involve high-impact activities, such as police officers, firefighters and the armed forces, or those who participate in activities such as boxing and martial arts.
The drawback with PRK is that it takes longer for the vision to recover and stabilize. There is also more discomfort after PRK surgery, which can last up to four or five days, says Edward Jaoude, M.D., of Delaware Eye Clinics. However, the discomfort is allayed with a soft-bandage contact lens as well as drops and oral medications, Sumlin adds.
Both LASIK and PRK surgery can now take advantage of Wavefront technology that allows the eye surgeon to completely customize the laser correction treatment. Wavefront technology allows the surgeon to do a Wavescan of the eye that not only tells the surgeon the correction that needs to be made but also indicates other optical aberrations of the eye, Markowitz says. The Wavescan guides the surgeon in making a decision on the proper treatment to use.
“The Wavescan is basically like fingerprinting the cornea before treatment,” notes Jaoude. LASIK and PRK have also improved with the introduction of trackers, which are infrared cameras that lock on the position of the eye and follow its movement at a rate of 60 times per second, allowing the surgeon to deliver the wavefront-corrected treatment more precisely to the correct location on the cornea, Jaoude says. In the past, trackers could only follow the eye sideways, but in the past three or four years these trackers have been improved such that they can follow the eye in every 3-D direction of movement, he says.
At this point, there is no way to correct the vision to see better for both distance and near in patients older than 45 years, so some LASIK patients will still need reading glasses. However, there is the option of a MonoVision LASIK correction, in which one eye is corrected for distance and the other for near. MonoVision can take some getting used to, though. It can be tried out first using contact lenses in the office to see if the patient is a good candidate for this option, Jaoude notes.
Ophthalmologists stress that the decision on LASIK versus PRK surgery and details about the exact procedures to be used during surgery are very individualized and should be decided upon by the patient in consultation with the eye surgeon.
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