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THE SURGERY IS EASY
Laser vision treatment is a very easy procedure to undergo. No injections are needed, and there is no pain during the procedure. These are the steps you will experience:
1. Your doctor will measure your eyes to determine your amount of nearsightedness, farsightedness, and astigmatism. During this presurgical consultation, your doctor will complete a thorough examination of the health of your eyes and discuss the procedure in detail with you.
2. The laser will be calibrated and tested for accuracy.
3. The correction desired for your eye will be entered into the laser’s computer.
4. The computer will determine the specific set of laser pulses to apply.
5. You will be brought into the laser room and asked to lie down.
6. A patch will be placed over the eye not having the procedure.
7. Anesthetic eyedrops will be placed in the eye. No injections or IVs are needed.
8. Your eyelid will be held open with a small speculum, which causes no pain.
9. You will be asked to look at a small blinking light.
10. In Lasik, a small amount of tissue, known as the corneal flap, will be separated and lifted. In PRK, the doctor will gently wipe away the most superficial layer covering the cornea.
11. You will hear a clicking noise, the sound of the laser.
12. The blinking light will get hazy as the treatment progresses.
13. The treatment will usually take less than thirty seconds of laser time.
14. Eyedrops will be placed in the eye. In some cases, a temporary contact lens will be placed in the eye as well.
15. In most cases, the procedure will then be repeated for the second eye.
16. You will sit up and rest for a few minutes before going home. Your stay in the treatment room has lasted about five to ten minutes.
Sounds easy, doesn’t it? And it is. But how accurate are the results? What can go wrong? Are you a suitable candidate for laser vision correction, or should you consider alternatives? These questions will be addressed shortly. First, we will examine the mechanics of the eye.
HOW DOES THE EYE WORK?
Just like a camera, the eye works by focusing light rays. Light entering the eye first passes through a transparent layer called the cornea. The cornea acts as a lens by focusing the light. Located behind the cornea is another lens, known as the crystalline lens, that further focuses the light to make a clear image on the retina at the back of the eye. Finally, the image is transmitted to the brain by the optic nerve.
Just as a camera cannot produce a clear photograph if the incoming light is not focused precisely onto the film, so the eye cannot produce clear vision if the cornea and crystalline lens do not focus the light precisely onto the retina.
The eye is very similar to a camera. Light rays are focused by the cornea and crystalline lens. The focus must be accurate in order to obtain a clear image.
COMMON VISION PROBLEMS
The most common vision problem is the inability to focus incoming light precisely onto the retina. The result is blurred vision.
There are four types of focusing errors:
Nearsightedness. Nearsighted people see near objects more clearly than objects farther away. In nearsightedness (also known as myopia), light rays from distant objects are focused not onto the retina but in front of the retina. Nearsightedness occurs because the cornea and the crystalline lens together have too much focusing power for the length of the eye. If the cornea and the crystalline lens had less combined focusing power, or if the eye were shorter, then the light rays would be focused precisely onto the retina.
Farsightedness. Farsighted people see faraway objects more clearly than they see nearby objects. In mild cases of farsightedness, or in younger people, only near objects will be blurry. In moderate cases, or in older individuals, both far and near vision will be blurry, but the near vision will be more affected. Farsightedness (also known as hyperopia) results when the cornea and crystalline lens together have too little focusing power for the length of the eye. Light rays from distant objects are focused not onto the retina but behind the retina. If the cornea and the crystalline lens had more combined focusing power, or if the eye were longer, then the light rays would be focused precisely onto the retina.
Astigmatism. People whose eyes focus light rays unevenly have astigmatism. Astigmatism occurs when the cornea has an irregular shape. The cornea should be round and symmetrical like a basketball, but in cases of astigmatism it is shaped more like a football or the back of a spoon. People with astigmatism see both near and far objects out of focus. Astigmatism frequently accompanies nearsightedness or farsightedness.
Presbyopia. Presbyopia (which comes from the Greek for “old vision”) refers to the gradual loss, as we age, of the eye’s ability to adjust the focus from far to near. Presbyopia is a normal part of the aging process, affecting each and every person, and usually begins to cause a problem with near vision between the ages of forty and fifty. It is corrected by the use of reading glasses or bifocals. Presbyopia occurs because the crystalline lens no longer adequately adjusts its shape to focus clearly on close-up objects.
Presbyopia is referred to as “farsightedness” by most people and is frequently confused with true farsightedness (hyperopia). Presbyopia and hyperopia are often confused because both compromise up-close vision, though in entirely different ways. Presbyopia is an age-related loss of flexibility of the crystalline lens. Hyperopia is caused by too little focusing power in the eye—a combination of the cornea, the crystalline lens, and the length of the eye. Whereas presbyopia is an aging effect that begins to be experienced sometime after thirty-five years of age, hyperopia affects people of all ages, even young children.
Presbyopia can be present by itself or in combination with nearsightedness, farsightedness, or astigmatism.
In ancient times, people with focusing errors had to live with blurry vision. During the late Middle Ages (around a.d. 1250), the first glasses were developed. For almost seven hundred years, glasses were the only treatment available for focusing errors. In the 1930s, hard contact lenses were developed, followed in the 1970s by soft contacts.
Glasses and contact lenses improve vision by helping the eye to focus the incoming light rays. They subtract focusing power from nearsighted eyes and add focusing power to farsighted eyes. Bifocal lenses help people with presbyopia to see faraway objects (through the upper portion) as well as near objects (through the lower portion).
From the Trade Paperback edition.