Frequently Asked Questions About Excimer Laser Refractive Surgery
1. What is excimer laser refractive surgery?
Laser refractive surgery is one of several refractive surgery procedures used by ophthalmologists to change the shape of the cornea, the clear tissue window at the front of the eye, to improve the way it focuses or "refracts" light to receptors at the back of the eye. The excimer laser produces ultraviolet light and emits high-energy pulses lasting only billionths of a second. In excimer laser refractive surgery, the ophthalmologist uses this laser energy to carve away minute amounts of corneal tissue.
2. What is the medical condition that is treated by excimer laser refractive surgery?
Ophthalmologists use excimer laser refractive surgery to treat nearsightedness, or myopia, a condition where the eye is too long and images are focused in front of the receptors (the retina) at the back of the eye. This causes distant images to appear fuzzy. Most commonly, this condition is treated with spectacles or contact lenses, which change the way light is "refracted" to the retina. Approximately 70 million people in the United States -- one in four -- have varying degrees of myopia.
3. How does the procedure work?
The front of the eye is covered by a clear tissue called the cornea. The shape of the cornea helps determine how light is focused on the retina. Using the excimer laser, the ophthalmologist removes microscopic layers of corneal tissue from the surface of the cornea to change its shape and improve the focus of light images. This can eliminate or reduce a person's reliance on corrective lenses to view distant images. The process is formally called photorefractive keratectomy, or PRK.
4. What is involved in a laser refractive surgery operation?
The ophthalmologist determines the correction required (which is measured by the same examination used to prescribe spectacles or contact lenses) and programs the correction into the laser's computer. The ophthalmologist then uses instruments to manually remove the thin layer of cells covering the outer surface of the cornea (the epithelium).
The laser surgery itself lasts about 30 seconds, during which the ophthalmologist operates the laser and monitors the patient to ensure that the eye is properly aligned. The entire operation, including patient preparation and post-operative dressing, generally lasts no more than 20 minutes. A patient typically has one eye treated in a session, with the second eye treated after the first eye has recovered.
After the operation the ophthalmologist may prescribe topical drugs to promote corneal healing and alleviate pain. Patients generally experience blurred vision and discomfort until the epithelium regrows, usually within 48 to 72 hours after the procedure. Visual acuity may continue to fluctuate, but normally stabilizes within two to six months after the procedure. It is performed on an outpatient basis at the ophthalmologist's office or at a clinic.
5. Who is eligible for the procedure?
FDA restrictions will limit the procedure, at least initially, to those with low to moderate levels of myopia. In addition, persons undergoing the procedure should be old enough, usually about 20 years of age, that the vision corrections they require have stabilized. Women who are pregnant or people with certain medical conditions may not be good candidates for the procedure.
6. How successful is the procedure? Will I be able to throw away my glasses?
Approximately 94 percent of people with mild to moderate myopia who undergo laser refractive surgery are able to pass a drivers' license vision test without corrective lenses. That percentage increases for patients who are given additional laser treatments. Patients are very likely to not need glasses, but rarely a patient will want glasses to help with any left over refractive error (prescription need) that may persist.
7. Are there ever any complications?
Although rare, complications can occur as with any surgical procedure. Possible complications of laser refractive surgery include over- and under-corrections that may require additional operations, although this is rare among those who seek correction for low to moderate myopia. Patients may experience minor light sensitivity, glare, and night "halos" around images for several weeks after the operation.
In very rare cases, patients may experience a persistent haze that may take up to three years to clear.
8. Are there alternatives to this procedure?
Corrective lenses, either eye glasses or contact lenses, are the most common methods of correcting nearsightedness. Other surgical alternatives are radial keratotomy and automated lamellar keratectomy.
In radial keratotomy, the ophthalmologist makes a series of radial incisions in the cornea. In automated lamellar keratectomy, the ophthalmologist creates a flap with the top of the cornea, slices off a micro-thin piece, and then replaces the flap. Both techniques flatten the cornea to improve the way distant images focus on the retina.
A third procedure, still under investigation in the United States, combines the excimer laser with the automated lamellar keratectomy. This combined procedure is called laser assisted in situ keratomileusis, or LASIK.
9. What advantage does the excimer laser offer?
Most of the laser-light generated by the excimer laser is absorbed by the tissue that is removed from the cornea. Unlike some laser procedures, the process does not create a great deal of heat, limiting the possibility of thermal damage to surrounding tissue. These attributes make excimer lasers well-suited to corneal surgery. The excimer is also very precise, with each pulse able to remove 0.25 microns of tissue. A human hair is about 50-100 microns thick.
Е Copyright 1996 American Academy of Ophthalmology