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HOW THE EYE WORKS How clearly you see depends in large part on the shape of your cornea. This structure is the clear covering of the eye, which you look through. In the normal eye, your cornea helps to focus light rays directly on the retina (which acts like the film in a camera). If the eye is not shaped correctly, the image will fall in front of or behind the retina, causing images to be blurry. Myopia In myopia (nearsightedness), the distance from the cornea to the retina is too long. This causes the image to fall short of the retina, making images blurry. Astigmatism With astigmatism, the cornea is oval shaped instead of round. This makes both distance and near objects look distorted. Hyperopia In hyperopia (farsightedness), the distance between the cornea and the retina is too short. This causes the image to fall behind the retina, making images blurry. How refractive surgery changes vision Glasses and contact lenses work by bending light rays before they hit the cornea. The light rays are then focused directly on the retina , resulting in clear images. Refractive surgery changes the shape of the cornea itself, so it can bend the light rays to focus more directly on the retina without the use of contacts or glasses. These procedures can, therefore, reduce your dependence on your contacts or glasses and may help you get rid of them completely for most daily activities. They will not, however, stop you from needing reading glasses if you are over 40, even if you did not need them prior to surgery. PRK PRK (photorefractive keratectomy) is an FDA approved procedure that can be used to help people with mild to moderate nearsightedness, with or without astigmatism. During PRK, a computer controlled excimer laser is used to re-shape your cornea an amount determined to correct your vision. The procedure itself works by removal of layers of tissue, one by one, from the surface of the cornea. Its like taking one sheet of paper off a tablet at a time. This tissue removal causes the center of the cornea to become flatter, causing light rays to focus more directly on the retina. The FDA results showed that 96% of patients had 20/40 vision or better without contacts or glasses ,after excimer laser surgery. After the procedure, there is mild discomfort for 2-3 days. Vision is reasonably good after 1 week, but improves to maximal levels by 3 weeks , becoming stable by 3 months. LASIK LASIK (Laser in Situ Keratomileusis ) is a combinaton of two procedures. First, a special instrument called a keratome is used to create a flap of corneal tissue on the surface of the eye. This is much like a carpenters wood plane elevating a sliver of wood or like splitting a layer cake in two halves. The excimer laser is then used to reshape the bottom layer, in the same manner as described for prk. The corneal flap or upper layer is then placed back in its original position, covering the lasered area. The eye holds the flap in place naturally and sutures are rarely needed. The resulting flattening of the cornea again causes light rays to focus more directly on the retina, making images clearer, as in PRK. The advantages of this procedure are less post-operative discomfort and faster visual recovery--usually 1-2 days. Complete healing takes up to 3 months as in PRK. This is not an FDA approved procedure and no long term studies have been published as yet, but are being conducted by our staff and others around the country. Monovision In both the LASIK and PRK procedures, one eye can be partially corrected, while the other eye is fully corrected. The partially corrected eye can then be used for reading while the fully corrected eye is used for distance. This means that only one eye at a time is seeing clearly, depending on whether you are looking close or far away. This procedure is only done on patients over 40, usually after a trial of monovision with contact lenses. This is a special situation which should be discussed with your doctor if you are interested . Fees and Insurance It is always a good idea to know the costs prior to surgery and if it’s covered by insurance. Most insurance companies will not cover the PRK or LASIK procedure to correct myopia/hyperopia or astigmatism. In most cases, the responsibility will be the patient’s. We request payment or financial arrangements be made prior to the procedure being performed. We have multiple financing arrangements including one year interest free loans. Please ask our trained staff about these arrangements if you are interested. Potential complications and side effects 1. Delayed epithelial or poor epithelial healing which can lead to scarring, vision loss and further surgery. 2. Under or over correction which may lead to further surgery or may not be correctable 3. Nite halo can occur with PRK and LASIK and has an increased incidence when astigmatism is corrected. This usually fades with time, but may be permanent. 4. Llight sensitivity can occur for a short time after these surgeries. This usually fades with time but can be permanent. 5. Corneal haze or scarring can occur with these procedures. It is usually less with LASIK than PRK. This usually diminishes with time and does not effect the vision but in some cases may be permanent and or effect vision. 6. Eye co-ordination: when both eyes need correction, there is a problem with eye co-ordination after surgery has been done on one eye. Wearing glasses, a patch or contact lens may be necessary until both eyes can be corrected. 7. Contact lens tolerance may be diminished after these procedures 8. Bilateral surgery (both eyes) entails all the same risks as single eye surgery, however, if complications do occur, they may effect both eyes leading to loss of vision in or loss of both eyes. 10. Infection can occur in these procedures and can be blinding or lead to loss of an eye(s) 11. Unknown or unanticipated complications can occur with these procedures leading to loss of vision or loss of an eye(s) at present or in the future.
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