Refractive Errors and Laser Vision Correction (please see videos for additional information)
Refractive errors occur when light does not focus properly on the retina because of the shape of the eye. The resulting image is blurred. Common refractive errors are myopia (nearsightedness), hyperopia (farsightedness), astigmatism (distorted vision), and presbyopia (aging eyes).
A myopic eye is longer than a normal eye or has a cornea that is too steep, causing light rays to focus in front of the retina instead of on it. With myopia, close objects appear clear, but distant ones appear blurred.
A hyperopic eye is relatively short or has a cornea that is relatively flat. The light rays focus beyond the retina instead of on it. Distant objects appear clear, but close ones appear blurred.
The cornea of an astigmatic eye is curved unevenly. Images focus in front of and beyond the retina, causing both close and distant objects to appear blurry.
Presbyopia refers to the changes of the lens that occur with age. After approximately 40 years of age, the lens does not change shape as easily to accommodate near objects. This makes reading and other tasks performed at close range more difficult. Presbyopia can occur in combination with any of the other three refractive errors.
Treatment of refractive error
Refractive errors are usually corrected with eyeglasses or contact lenses. Sometimes surgery is needed or desirable. Some common surgical procedures include the following:
This popular procedure involves creating a flap in the cornea so that the underlying corneal tissue can be reshaped with a laser.
Photorefractive Keratectomy (PRK)
Photorefractive keratectomy sculpts the surface of the cornea using a laser. A “bandage” contact lens is then applied for about three days to allow it to heal.
Intrastromal Corneal Rings
Intrastromal corneal rings are crescent-shaped plastic segments implanted in the cornea to flatten the cornea and correct mild nearsightedness. However, this technique is now used more commonly to treat a condition called kerataconus, in which the cornea becomes irregular in shape. It is no longer a standard treatment for vision correction.
What approach is best for you?
In order to determine which is the best technique to correct your vision, a thorough evaluation is required. This evaluation includes not only an assessment of your visual needs and activities, but also multiple diagnostic tests that assess factors such as the shape and thickness of your cornea. The purpose of this testing is to ensure the safety of any procedure being considered.