LASIK and Laser Vision Correction

By Joseph A. Eviatar, MD

Published on July 20, 2006

For over 25 years, doctors placed incisions in the cornea to treat nearsightedness, farsightedness and astigmatism. In the 1970's, a more precise mode of incisional corneal surgery became popular for treatment of myopia. While effective in reducing myopia, the procedure was not precise enough to satisfy most patients and physicians. In the early 1980's, the excimer laser was developed to precisely remove corneal tissue with up to 0.25 microns of accuracy. Now in its second decade of use, ophthalmologists use the excimer laser to reshape the cornea according to a patient's eyeglass or contact lens prescription, thereby reducing or eliminating the patient's need for corrective lenses. Most of the patients who have laser vision correction see 20/20 after the procedure and 98% do not require glasses for most activities and can pass a drivers license test without their glasses or contact lenses.

LASIK, or Laser in-Situ Keratomileusis, offers a number of benefits over other forms of laser vision correction because it is performed under a protective layer of corneal tissue. The first laser correction procedure approved by the FDA was Photorefractive Keratectomy (PRK). During this procedure, the surgeon applies the excimer laser beam to the surface of the cornea. While effectively reshaping the cornea in most patients, the procedure requires several days of healing time, discomfort and a longer period until visual rehabilitation is achieved. Also because of the increased need for healing, there is a greater chance of development of corneal scar tissue (haze) and a possibility of blurry vision. During LASIK, a microkeratome is used to create a thin flap of corneal tissue and the laser treatment is performed under this tissue layer. As a result, there is less surface area to heal, less risk of scarring, less risk of corneal haze, less postoperative discomfort, less postoperative need for medications, and vision returns more rapidly, often within a day. LASIK can be used to treat a higher range of vision errors including nearsightedness, farsightedness, and astigmatism. Most patients have both eyes treated at the same time and return to work the following morning.

LASIK became popular during the 1990's due to the enhanced safety of microkeratomes. Advances in technology allowed for safer designs of these instruments, which helped minimize the chances for complications, associated with development of the surgical flap. Today's microkeratomes are designed to minimize technician and surgeon error and provide an extremely high safety profile when used by experienced surgeons.

During the procedure, the eye is completely numbed using eyedrops and an eyelid holder is used to prevent blinking. Next, the microkeratome makes a protective flap in the cornea in about 10 seconds. During this process, the patient may feel a little pressure but no pain. The patient is then asked to look directly at a target light while the laser reshapes the cornea, usually in less than a minute. The protective flap is then folded back in place where it bonds securely without the need for stitches. After LASIK, patients are asked to rest for several hours. They must refrain from rubbing their eyes. Some patients report a slight discomfort that usually resolves within several hours after the procedure. Most patients have improved vision within several hours and are able to return to work the following day.

To treat nearsightedness, the cornea is made flatter. To accomplish this, the laser removes tissue from the center of the cornea. To treat farsightedness, the central cornea is made steeper by directing the laser beam to remove tissue from the peripheral cornea. To treat astigmatism, the cornea must be made more spherical; by changing the pattern of the beam, tissue is removed in one direction more than the other.

After the procedure, patients are asked to sleep with protective shields for 3 nights and must avoid swimming with their head under water for 2 weeks. They may resume all other activities by the next morning including exercising, flying in airplanes, and computer work. Patients are told to expect some dryness in their eyes for several weeks after the procedure and are treated with lubricating eyedrops until the dryness resolves. Many patients experience some nighttime halos during the first few days after the procedure, especially patients with higher levels of correction and larger pupil sizes. These patients may need to refrain from night driving for several days.

Are You a Candidate for LASIK?

The ideal candidate for LASIK is over 18 years of age and has healthy corneas. Candidates must not have had a significant increase in their prescription in the last 12 months and people with certain medical conditions may not be good candidates for LASIK. These include certain autoimmune disorders, diseases of the cornea and pregnancy. It is important the patients have realistic expectations and that the decision to have the procedure be based on facts, not hopes or misconceptions. The goal of LASIK is to reduce dependence on corrective lenses but LASIK does not always create 20/20 or even 20/40 vision. It cannot correct a condition known as presbyopia, or aging of the eye. This normally occurs after age 40 and usually requires the use of reading glasses. Certain patients may be at higher risk for potential side effects of the procedure. For example, patients with dry eyes may have prolonged healing times and may benefit from a temporary procedure to close the tear duct opening (punctal plugs) prior to the procedure. Patients over 40 may benefit from a slight undercorrection in one eye to help delay the need for reading glasses or from monovision (where one eye is corrected for reading and the other for long distance). It is important for these patients to spend time with their doctor discussing their specific visual needs (i.e. occupational, recreational) so that the ideal level of correction can be achieved. Most patients who have LASIK are thrilled and consider it a life altering experience.

As with any surgical procedure, there is always a chance of a rare complication. Enhancements are needed in approximately 5% of patients. An enhancement is performed if there is under or over correction and is usually performed by simply lifting the flap and providing some more laser treatment. Vision loss, while extremely rare, is possible. About 1% of patients may have slightly less sharp vision, which is not improved with glasses or contact lenses, after the procedure. This may occur from any of the following complications. Surgical complications include problems with the flap such as misshapen or moved flaps, scratches to the surface of the cornea, poor centeration of the laser beam, and malfunctions of the microkeratome or laser. With proper care, most surgical complications can be successfully treated. Treatment may include re-cutting the flap, repositioning the flap, and the use of a bandage contact lens (to aid in healing). Infection and inflammation are possible and require treatment with eyedrops. A rare form of inflammation, diffuse intra-lammellar keratitis (DIK) may require the use of steroid eyedrops for several weeks and possibly lifting and irrigating fluid under the flap. While extremely rare, these complications can cause some loss of vision if not treated promptly. For this reason, it is important that patients seek qualified physicians who have experience with LASIK and practices that offer comprehensive eyecare services.

For more information on the author, please visit www.chelseaeye.com