We hope that we can answer your questions to help you in the care of your eyes. Thank you for consulting EyeCareUSA.
This page is not intended to subsitute for visits to your eye care specialist, but merely serves as a complementary service. If you have any unanswered questions after reading this material, please call your ophthalmologist.
REFRACTIVE SURGERY - RK, AK, AND LASERS: Clear vision is the result of light rays passing through the cornea, pupil and lens and focusing precisely on the retina. If the cornea is not perfectly round or spherical, or is too steep or too flat in relation to the length of the eye, light rays focus either in front of or behind the retina resulting in "refractive errors" such as nearsightedness, farsightedness and astigmatism. Refractive surgery is the term for several procedures designed to treat these vision abnormalities. The following discussion will explain how refractive surgery attempts to alter the way your eye focuses light by changing the shape of your cornea.
Since the late 1970s, advances in technology and surgical technique have made refractive surgery more predictable, with the vast majority of patients having their vision corrected to 20/40 or better.
Refractive surgery is done on an out-patient basis with most people returning to their normal activities within one to three days. Your doctor will help you decide which procedure or combination of these procedures is best suited for you.RK: Radial Keratotomy is most effective when treating low to moderate levels of nearsightedness. A person is considered nearsighted when their eye is too long or their cornea too steep to allow light to focus directly on the retina. Instead light focuses in front of the retina causing distant images to appear blurry.
Your refractive surgeon will change your cornea's curvature by making a number of tiny spoke-like incisions in a "radial" pattern around the edge of the cornea leaving the central portion untouched. This causes the central cornea to flatten a predicted amount which allows light to focus more precisely on the retina, thereby reducing nearsightedness.
AK: Astigmatic Keratotomy can be viewed as a modified form of Radial Keratotomy. Regular astigmatism occurs when the cornea's shape is like the back of a spoon or a football, more curved in one direction than the other. Light entering the cornea focuses in more than one point within the eye resulting in blurry and distorted vision. Astigmatism is often found in combination with nearsightedness and farsightedness and can be both regular and irregular in form.
To treat astigmatism, the cornea must be made spherical, like a basketball. This is done by making several microscopic incisions in the steepest part of the cornea causing it to relax and become more round. Astigmatic Keratotomy is often performed in combination with other refractive procedures.
PRK: Photo-Refractive Keratectomy is another method of surgically reshaping your cornea using the excimer laser. Ultraviolet light and high energy energy pulses lasting only billionths of a second disrupt the molecular bonds between the corneal cells with accuracy up to 0.25 microns. The escimer laser is unique in that it emits a "cold" or non-thermal light beam. This makes it ideal for corneal surgery because it eliminates the possibility of thermal damage to surrounding tissue.
In less than a minute, the excimer laser, with computer controlled precision, removes microscopic amounts of corneal tissue from the surface of the cornea, making the central zone flatter. The flattened cornea is then able to focus light more precisely on the retina, thereby reducing nearsightedness. The procedure is performed under topical (drop) anesthesia.
LASIK: Laser Assisted In-situ Keratomileusis, also known as Laser Intrastromal Keratomileusis, combines the precision of the excimer laser with the benefits of lamellar keratoplasty. Lamellar keratoplasty is performed with an automated microkeratome which lifts up a thin layer of the cornea, or corneal cap, revealing the stroma, or deeper layer of the cornea. Then in less than 60 seconds, ultraviolet light and high energy pulses from the excimer laser reshape the internal cornea with unparalleled accuracy. After the tissue has been reshaped, the flap is replaced in its original position and adheres without requiring stitches. The LASIK procedure can treat moderate to high levels of myopia, and modification of the laser patterns allow treatment of farsightedness and astigmatism. LASIK is still considered "investigational" by the FDA but is rapidly becoming the procedure of choice of refractive surgeons all over the world.
If you have any further questions regarding Refractive Surgery, please consult your eye specialist.
