Information provided by the American Academy of Ophthalmology
The Eye M.D. Association
REFRACTIVE SURGERY: A CLOSER LOOK
LASIK and epi-LASIK
LASIK is a combined microsurgical and excimer laser procedure used to correct nearsightedness (myopia), farsightedness (hyperopia) and astigmatism. In LASIK, either a laser or a highly specialized instrument, a microkeratome, is used to make a thin flap in the cornea. The excimer laser is applied beneath the corneal flap. The flap is then replaced and allowed to heal. No stitches are necessary.
Epi-LASIK (epithelial LASIK) is a refractive surgery procedure used to treat nearsightedness (myopia), farsightedness (hyperopia) and astigmatism. Epi-LASIK is similar to LASIK in that a flap is made with a keratome or mechanical device. But the flap with Epi-LASIK is much thinner and may be more appropriate for patients with thin corneas who would not otherwise be candidates for the conventional LASIK procedure.
The epi-LASIK procedure uses a specific type of a microkeratome, called an epi-keratome. The epi-keratome, precisely separates the thin epithelial sheet – much thinner than a LASIK flap – from the rest of the cornea. Once the epithelium is separated from the rest of the cornea, the thin sheet of epithelial cells is lifted to one side. After a laser is used to treat the cornea, the thin sheet is then moved back into place, where it will self-adhere. After the procedure, a transparent bandage contact lens is placed on the cornea to promote healing.
Advanced surface ablation (PRK and LASEK)
Advanced surface ablation (ASA) is a refractive surgery technique used to treat nearsightedness (myopia), farsightedness (hyperopia) and astigmatism. With ASA, the outermost layer of the cornea, the epithelium, is removed or displaced to expose the stroma (the middle, thickest layer of tissue in the cornea). A computer-controlled excimer laser then reshapes the front surface of the corneal stroma. The epithelium is either replaced or assisted in healing back over the surface of the cornea underneath a bandage contact lens. ASA is usually recommended instead of LASIK for people with thin corneas. ASA procedures include photorefractive keratectomy (PRK) and laser epithelial keratomileusis (LASEK).
PHOTOREFRACTIVE KERATECTOMY (PRK)
With PRK, the surgeon removes micro-thin layers of tissue from the outermost layer of the cornea, the epithelium. When treating myopia, or nearsightedness, the surgeon then uses the laser to remove central corneal tissues in a circular pattern, thereby flattening the cornea and weakening the focusing power of the eye. The tissue is removed in a controlled pattern programmed into the computer by the surgeon. When treating hyperopia, or farsightedness, the surgeon uses the laser to remove peripheral corneal tissue, thereby steepening the central cornea to increase the focusing power of the eye.
In comparison, when treating astigmatism, the laser is programmed to remove tissue in an elliptical patter, selectively reshaping some portions of the cornea to form a smooth symmetrical surface. This procedure requires precise evaluation of the astigmatism so that the correct amounts of laser energy are delivered to the appropriate areas of the cornea. PRK is often a better option for people whose occupation makes it more dangerous to have a flap, as it could be dislodged accidentally.
LASER EPITHELIAL KERATOMILEUSIS (LASEK)
With LASEK, your ophthalmologist (Eye M.D.) uses an alcohol solution to loosen and peel back the epithelium to expose the cornea. The excimer laser then results the cornea, and the epithelium is placed back into position. After the procedure, a transparent bandage contact lens is placed on the cornea to promote healing.
Are you a good candidate for refractive surgery?
You might consider refractive surgery if you:
- Wish to decrease your dependence on glasses or contact lenses;
- Are free of eye disease;
- Can accept the inherent risks and potential side effects of the procedure;
- Have the appropriate refractive error.
While refractive surgery does offer some people an alternative to dependence on glasses or contact lenses, it’s not for everyone. You may not be a good candidate for refractive surgery if you are generally satisfied with glasses or contact lenses and unwilling to accept to uncertainty in the outcome of refractive procedures. Even after refractive surgery, certain people may still need to wear glasses or contacts. Surgery, contacts and glasses each have their benefits and drawbacks. The best method of correcting your vision should be decided after a thorough examination and discussion with your ophthalmologist.