For those with refractive errors, LASIK offers an alternative to eyeglasses and contacts for correcting vision. First approved by the FDA in 1998, LASIK is the most commonly performed refractive surgery in the U.S., with an estimated 700,000 people electing to have the surgery every year. The arrival of LASIK and other forms of refractive surgery has helped improve the vision of millions of people with myopia (near-sightedness), hyperopia (far-sightedness), and astigmatism (a cornea with unequal curves).
Laser assisted in situ keratomileusis, or LASIK, corrects refractive errors using an automated blade and laser to permanently reshape the cornea. The reshaped cornea helps focus light directly onto the retina to produce clearer vision.
LASIK is generally performed as an outpatient procedure using topical anesthetic drops, and the procedure itself generally takes about fifteen minutes to complete. The surgeon creates a flap in the cornea using an instrument called a microkeratome. The flap is lifted to the side, and the cool beam of the excimer laser is used to remove a layer of corneal tissue. The flap is folded back into its normal position and sealed without sutures. The removal of corneal tissue permanently reshapes the cornea.
A shield protects the flap for the first 24 hours following surgery. Vision is generally clear by the next day. Healing after surgery is often less painful than with other methods of refractive surgery since the laser removes tissue from the inside of the cornea and not the surface. If needed, eye drops can be used for pain and are usually only necessary for up to one week.
It is estimated that 90% of patients who undergo LASIK achieve between 20/40 and 20/20 vision, and the procedure itself has a 95% patient satisfaction rate. As the technology has improved, so have the outcomes, however, LASIK is not without risks. Some people experience poor night vision after LASIK. The surgery may result in undercorrection or overcorrection, which can often be improved with a second surgery. More rare and serious complications include a dislocated flap, epithelial ingrowth and inflammation underneath the flap. Most complications can be managed without any loss of vision. Permanent vision loss is very rare.
The ideal candidate for LASIK has a stable refractive error within the correctable range; is free of eye disease; is at least eighteen years old; and is willing to accept the potential risks, complications and side effects of LASIK.
Photorefractive keratectomy (PRK) is a type of laser eye surgery that permanently changes the shape of the cornea, improving the way it focuses light on the retina. Before LASIK, PRK was the most commonly used form of refractive surgery, and although the two procedures share some similarities, each is performed differently and has its own distinct set of advantages and disadvantages.
Like LASIK, PRK is used to correct myopia, hyperopia and astigmatism by reshaping the cornea. However, one of PRK’s advantages is that it’s used on the surface of the cornea, not underneath, as in LASIK. PRK requires no incisions, leaving the structural integrity of the cornea intact.
During PRK surgery, thin layers of the epithelium, or the outer cell layer of the cornea, are removed with cool ultraviolet beams of an excimer laser. By breaking the bonds that hold the tissue molecules together, the cornea is reshaped, correcting the refractive error. Immediately following surgery, either a patch or a bandage contact lens is placed on the eye for protection.
Patients may have some discomfort for the first few days following surgery, and vision will remain blurry anywhere from three days to a week. It often takes a month or longer to achieve best vision, and eye drops may also be required for an extended period. The extended recovery time for PRK versus LASIK is often cited as one of the procedures greatest disadvantages.
Possible complications of PRK surgery include undercorrection, overcorrection, poor night vision and corneal scarring. Permanent vision loss is very rare. In studies monitored by the FDA, 95% of eyes were corrected to 20/40, the legal limit for driving without corrective lenses in most states.
PRK still remains the preferred method of refractive eye surgery for patients with thin corneas and large pupils. It is also highly effective in treating extreme near-sightedness and may offer an alternative to those who are otherwise not good candidates for LASIK. Candidates for PRK must have a stable and appropriate refractive error; be free of eye disease; at least eighteen years old; and willing to accept the potential risks, complications and side effects of PRK.