university eye surgeons

EXCITING RECENT DEVELOPMENTS
IN REFRACTIVE SURGERY

Because of new improvements in surgical and laser technology, exciting opportunities exist for patients who wish to decrease their dependence on glasses and contact lenses. Radial keratotomy has been available for the treatment of nearsightedness for almost 20 years. In 1995, after nearly 10 years of experimental development, the Excimer laser was approved by the FDA for the treatment of nearsightedness using a technique called photorefractive keratectomy (PRK). More recently, the Excimer laser has been used in conjunction with a surgical device called a microkeratome to perform a newer procedure called LASIK (LAser in SItu Keratomileusis). These developments now allow surgery to correct nearsightedness, farsightedness, and astigmatism with greater safety and accuracy than ever before.

HOW DOES REFRACTIVE SURGERY WORK?

Almost all refractive surgery today works by changing the curvature of the cornea. In radial keratotomy, partial thickness incisions are made in the outer part of the cornea with a diamond blade; this allows the central part of the cornea to flatten, thus reducing nearsightedness. In PRK, the laser actually removes tiny amounts of tissue from the central cornea, thus changing its curvature. In LASIK, the microkeratome cuts and temporarily lifts away the front layer of the cornea. The laser then removes some of the tissue under the frontal layer. When the front layer is replaced in its original position, the cornea has a new curvature. The computer which controls the Excimer laser for PRK and LASIK can be programmed to remove tissue in such a way that nearsightedness and farsightedness, along with astigmatism, can be reduced.

IMPORTANT DEFINITIONS

Nearsightedness or myopia refers to a condition in which patients cannot see clearly at distance without correction. Nearsightedness is measured in diopters. The more negative the number, the more nearsighted the patient. For example, a -2 diopter myope can see an object held at arms length, but no further. A -10 diopter myope can see clearly approximately 4 inches away from the eye and no further. Nearsightedness is corrected by flattening the cornea.

Astigmatism occurs when the cornea is shaped more like a football than a baseball; one part of the cornea is steeper than another part of the cornea. Astigmatism causes blurred vision at all distances and is also measured in diopters. Astigmatism is corrected by flattening the steeper parts of the cornea more than the other parts of the cornea.

Farsightedness occurs when a magnifying lens is required to see objects at distance and near. It is measured in positive diopters. Farsightedness is corrected by steepening the cornea.

Presbyopia occurs when a patient, typically around age 43, loses the ability to change focus from distance to near. This condition is corrected with bifocals or reading glasses. Presbyopia cannot be corrected with refractive surgery. In other words, if a person age 50 has perfect distance vision after refractive surgery, reading glasses will be required for near vision.

WHAT ARE THE ADVANTAGES AND
DISADVANTAGES OF THESE PROCEDURES?

Radial keratotomy has the advantage of having been around the longest; thus it is the most well-studied. While radial keratotomy can be used to reduce mild to severe nearsightedness, certain side effects are more common when it is used to treat higher levels. These include a starburst effect around lights at night and fluctuation of vision in the morning to evening. Because of the rarity of side effects, quick recovery time, and least expense, radial keratotomy may be the most appropriate procedure for some patients with low levels of nearsightedness.

PRK was extensively studied by many different medical centers and companies prior to its approval by the FDA in 1995. Thus, while it is new compared to radial keratotomy, we have an extensive amount of information regarding its safety and effectiveness. The most common side effects of PRK, which include haziness of vision and halos around lights, are more common when it is used to treat the higher ranges of nearsightedness; these tend to decrease with time. It takes about two weeks for the surface of the eye to stabilize after PRK. For this reason, it is usually performed on only one eye at a time, with the second eye being done once the first eye has stabilized. PRK is most commonly used for the treatment of mild nearsightedness (1-4 diopters). PRK can also correct moderate levels of astigmatism and farsightedness.

When PRK was used to correct levels of nearsightedness greater than 7 diopters, one disadvantage was that the eye had a greater tendency to form scar tissue as part of the healing response to the removal of tissue by the laser. LASIK avoids this complication by allowing removal of tissue within the cornea rather than from the surface. Thus, LASIK can be used to correct much larger degrees of nearsightedness than either radial keratotomy or PRK. Another advantage of LASIK is that since the surface tissue is replaced in its normal position at the end of the surgery, the recovery time is extremely rapid, so that patient discomfort is minimized and surgery can be performed on both eyes at the same sitting if desired. Since LASIK requires the use of microkeratome technology and increased surgical skill on the part of the ophthalmologist, its cost is slightly higher than that of PRK. LASIK can be used to correct nearsightedness between 1-12 diopters. As with PRK, LASIK can also reduce moderate degrees of astigmatism and farsightedness.

HOW SUCCESSFUL ARE PRK AND LASIK?

Depending on the level of nearsightedness being corrected, 95% of the patients undergoing PRK or LASIK will be able to see 20/40 or better without glasses. While 20/40 is the level of vision required in most states to pass a driver’s license examination without glasses, some patients may still wear glasses or contact lenses after refractive surgery for certain tasks. As with all surgical operations, complications such as infection are rare, but possible. For this reason, it is important for the eye surgeon to follow the patient closely until healing has occurred. As with RK, it is sometimes necessary to re-treat an eye with PRK or LASIK if the patient has not gotten adequate correction with the first procedure. This is especially true when LASIK is used to correct extremely high nearsightedness

WHO SHOULD HAVE REFRACTIVE SURGERY?

Refractive surgery is recommended for people with nearsightedness, farsightedness, or astigmatism, who wish to decrease their dependence on glasses and contact lenses. Certain medical conditions and eye diseases make these procedures more risky. All of the ophthalmologists and optometrists associated with University Eye Surgeons are very familiar with the available forms of refractive surgery and can advise you as to whether you should consider refractive surgery. The final decision as to the advisability of refractive surgery and which procedure would be best for you is between you and the surgeon performing the procedure. Drs.Paul Froula, David Harris, Lee McDaniel and Kenneth Olander have extensive training and experience in all forms of refractive surgery, and are available for consultation with patients either by appointment or by referral from other ophthalmologists and optometrists.

A NEW OUTLOOK

We at University Eye Surgeons believe the addition of the Excimer laser and microkeratome technology provides new levels of safety and effectiveness for refractive surgery. This will give many more people the opportunity to see better without glasses or contact lenses. Ask your ophthalmologist or optometrist or contact University Eye Surgeons for a consultation to determine whether laser refractive surgery is appropriate for you.

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