Biology 103
2000 First Web Report
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Astigmatism is a condition, usually inherited, in which the cornea, or front surface of the eye, has an irregular shape. This is grouped with nearsightedness (myopia) and farsightedness (hyperopia) in a group of eye conditions called refractive errors. Astigmatism is usually accompanied by either myopia or hyperopia, simply because the specific errors that cause them are similar. In most cases of astigmatism, the cornea is "pinched" either horizontally or vertically, shaped more like a football than a basketball. The abnormal shape causes light rays to refract either in front of or behind the retina, instead of directly on the retina, resulting in two focal points instead of one. Astigmatism can also be caused by corneal scarring(1).

Scientists have not yet determined what causes the cornea to be irregularly shaped, but they have found that it tends to worsen with time. Thus, there are varying degrees of severity of astigmatism. The table below shows these degrees, measured in diopters (the standard unit of measurement for refractive errors) (2).

Mild Astigmatism-less than 1.00 diopters

Moderate Astigmatism-from 1.00 to 2.00 diopters

Severe Astigmatism-from 2.00 to 3.00 diopters

Extreme Astigmatism-greater than 3.00 diopters

The most common solution comes in the form of special glasses or contacts. The lenses in these glasses are specially designed to give clear vision by compensating for the "pinch," thereby changing the focal point of light in the eye so it focuses directly on the retina, as well as correct either nearsightedness or farsightedness(1). For example, if you look through one of these lenses, then turn the glasses 180 degrees, your vision will be distorted, while with regular glasses your vision wouldn't change. The special contacts, called Toric lenses, accomplish the same thing. Toric lenses are available in hard, soft, and disposable types, although they were originally only available in hard lenses. Some of them are even weighted slightly at the bottom to keep them sitting correctly on the eye(3).

Another option that is often considered, particularly for people with a higher degree of astigmatism, is surgery. There are several different procedures that can be used, both laser and incision. Astigmatic Keratotomy is an invasive procedure, during which the surgeon makes transverse incisions in the abnormally shaped parts of the cornea, restoring it to a more round shape. This usually either lessens or eliminates blurry and distorted vision(4). The other invasive surgery is corneal transplant. This procedure is similar to any other type of organ transplant; a regularly shaped cornea is taken from an eye donor and transplanted onto the patient's eye(4).

There are also two options for laser surgery: LASIK (Laser Assisted In-situ Keratomileusis) and PRK (Photorefractive Keratectomy). During LASIK surgery, the doctor cuts a thin flap in the cornea, lifts it up, and uses a type of laser called an excimer laser to remove small amounts of tissue from the cornea layers underneath, giving it the necessary round shape. This procedure is "ambulatory," meaning patients walk in, are operated on, and walk out again-in fact, it usually only takes a few minutes. There is no pain during the surgery, and the patient is awake the entire time. Afterwards, the flap heals quickly, vision improves within days, and most patients can go back to work the next day. PRK is essentially the same procedure, except the surgeon removes tissue from the front of the cornea instead of the under layers. This procedure is also ambulatory, painless, and the patient is awake the whole time. However, the healing process takes longer than with LASIK, and patients sometimes have to wear a "bandage contact" and use antibacterial drops. It also may take months for vision to improve, rather than days(6).

There are also natural options for correcting astigmatism, although they are not as popular, and not yet proven to work. There are numerous herbs, including Ginko Biloba, Cayenne and Ginger, and Grape Seed Extract, and dozens of vitamins, such as A, C, D, E, Zinc, Copper, Beta-Carotene and Riboflavin. There are also several homeopathics (natural substances which have been found to trigger healing mechanisms in the body) suggested, including Sulfur-Heel, Traumeel Tablets, and Phosphor-Homaccord(7).

Even more remote is the idea of "eye aerobics, " a regimen of exercises which will supposedly improve not only astigmatism, but near- and farsightedness as well. However, this exercises program only strengthens the six extraocular muscles that control eye position and movement. These muscles become unevenly developed by daily activities such as watching television and reading or looking at a computer screen, causing unbalanced pressure, which results in, distorted vision(8). It is unlikely that these exercises would have much effect on an already oddly shaped cornea.

Thanks to (almost) all of these methods of correction, astigmatism sufferers can begin to see clearly. After all, with today's technology, even severe astigmatics can have their vision restored to normal. Finally, even those who were born with abnormal eyes can see straight.

WWW Sources

2) Common Vision Problems-Astigmatism , on TLC Laser Eye Centers site.

3) Toric Contact Lenses: How toric contact lenses correct astigmatism , on AllAboutVision.com.

4) What is Astigmatism? , on Young Eye Institute site.

5) Pamphlets and Publications: Blindness and Visual Impairment Centre: Corneal Transplants , description of corneal transplant procedure.

6) Consumer Guide to LASIK and Corrective Eye Surgery , on AllAboutVision.com.

7) Your Suggested Dietary Supplements , herbs, vitamins and homeopathics for astigmatism.

8) Welcome to Adobe GoLive 4 , explanation of eye aerobics.

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