How The Eye Works
To better understand LASIK and how the microkeratome and excimer laser can be used to correct myopia, hyperopia, and astigmatism, a short review of how the eye works may be helpful.
When light enters the eye, it is bent by a clear, strong tissue called the cornea. The cornea, in effect, acts like a lens to focus incoming light onto the retina.
A person's vision is adversely affected when there is a problem with the refraction of light entering the eye. Myopia, hyperopia and astigmatism are three common types of refraction problems.
In myopia or nearsightedness, light entering the eye does not focus on the retina as it should, but instead focuses at a point in front of the retina. Myopia is frequently caused either by an eye that is too long, or by excessive curvature of the cornea. The result of myopia is that objects that are far away appear blurry, although objects that are "near" to the viewer can be seen in focus.
In astigmatism, the problem is not the length of the eye, but the fact that the cornea has two different curvatures and is shaped more like a football or basketball. This results in distorted vision. Often, people who have myopia also suffer from astigmatism.
In hyperopia or farsightedness, the image focuses beyond the retina. Hyperopia or farsightedness is frequently caused by an eye that iis too short or by excessive flattening of the cornea. The result of hyperopia is that objects that are far away and close up appear blurry- depending on the level of farsightedness.
The Lasik Procedure:
If you desire to have LASIK performed on one or both of your eyes, you must thoroughly understand the following:
During the LASIK procedure, you will be permitted to wear your regular clothes. A companion should accompany you to the laser center. You will not be given a general anesthetic, but may receive an oral medication to help you relax. The other medication that you will receive before and during the procedure are eye drops. (Anesthetic, antibiotic, steroid and/or non- steroidal, anti-inflammatory medications may be used as, as appropriate.) While allergic reactions to these medications are rare, please advise your doctor, and your surgeon, of any allergies you may have. You will be able to ask questions and talk to your doctor during the procedure.
In the laser room, you will be seated in a patient chair similar to that in a dentist's office. At this point, the laser's computer will already have been programmed with your prescribed correction. The chair will be adjusted to align your eye with the laser system and the operating microscope. This takes about five (5) minutes.
The skin around the eye to be treated will be cleansed with iodine prep and your other eye will be loosely tapes closed.
An instrument called an eyelid speculum will be placed between your upper and lower eyelids to prevent you from blinking.
Next, your surgeon will place the suction ring on your eye and the suction will be turned on. It is necessary to raise the pressure within your eye to approximately 65- mm HG (mercury) or greater for the automated corneal shaper to function properly. Once the suction has been turned on, your vision will temporarily dim. This is normal, indicating adequate suction has been achieved, and should last 1 to 5 minutes or until the suction is turned off.
If for any reason the proper amount of suction cannot be obtained, your surgery may have to be rescheduled. Once it has been assured that the adequate amount of suction has been achieved, the automated corneal shaper will be placed in the suction ring, passed across the cornea, and reversed. The suction will be turned off and the automated corneal shaper removed from the suction ring. The chair will be positioned under the excimer laser and the corneal flap will be folded back to expose the area of the cornea (stroma) to be treated with the excimer laser.
Next, your surgeon will ask you to stare at a red light overhead. (Occasionally, the red light may become difficult to see as the procedure progresses.) Your surgeon will activate the excimer laser and begin reshaping your cornea. While the laser is in use, you will be asked to keep your eye as still as possible. However, a small amount of eye movement will not affect the outcome of the procedure.
Total laser time for most patients is about 60 seconds per eye. Your surgeon will tell you how you are doing throughout the procedure.