Astigmatism is a focusing error caused by a unround or non-spherical cornea. If you imagine the cornea as the surface of a ball, a spherical cornea is like a bowling ball - smooth and completely round.
A cornea with astigmatism has the surface shape of a football - smooth, but more round in one direction that the other. This DIFFERENCE in roundness is astigmatism. The difference causes one part of the cornea to focus light rays differently that the other resulting in TWO focus points.
How does astigmatism affect my vision?
The vision from astigmatism can be described a blurred, warped, smeared, stretched, or double. This unfocused vision can be INDEPENDENT from focus problems of nearsightedness (myopia) or farsightedness (hyperopia).
How is astigmatism treated?
Glasses - Correct astigmatism by externally refocusing light rays to one focal point. The portion of glasses that corrects astigmatism is called a "cylinder" which is ground into the lens. When looking at an eyeglass prescription, the astigmatism correction value can be noted in the lens formula. For example, a prescription such as -1.00 -2.00 x 90, the -2.00 in the astigmatism correction value (cylinder) and the direction is 90 degrees. Glasses can also correct myopia and hyperopia at the same time if these focus problems exist.
Contact lenses - Correct astigmatism by externally refocusing light rays to one focal point. A "toric" contact lens is the special type designed to correct astigmatism. When looking at a contact lens prescription, the astigmatism correction value can be noted in the lens formula. For example, a prescription such as -1.00 -2.00 x 90, the -2.00 in the astigmatism correction value (cylinder) and the direction is 90 degrees. Contacts can also correct myopia and hyperopia at the same time if these problems exist.
Incisional refractive surgery - Corrects astigmatism by changing the physical shape of the cornea with 2 small incisions which allow the surface to become spherical through an "unwinding" or "relaxation" of tissue tension. The procedure is called AK or arcuate keratectomy. Using the previous lens formula example, the -1.00 -2.00 x 90 could be changed to a simple myopia prescription of -1.00. This myopia could further be treated with simple glasses, simple contacts, LASIK, or a vision implant.
LASIK refractive surgery - Corrects astigmatism by changing the physical shape of the cornea using a cool laser beam that removes tissue until the surface is perfectly round. The new shape allows light rays to focus to one point. Generally, astigmatism is treated (removed) at the same time as any other focusing problems (myopia or hyperopia) are treated during a laser vision surgery session.
Vision implant lenses - Correct astigmatism much like glasses or contacts. The internal implant toric lens refocuses light rays into one point as the rays pass into the eye. These small this lenses are inserted into the eye during an operation. The implant lenses can correct other focusing problems such as myopia and hyperopia.
Implant lenses with cataract surgery - Correct astigmatism much like glasses or contacts. The internal implant lens refocuses light rays into one point as they pass into the eye. This is accomplished during a routine cataract surgery when the cloudy natural lens (cataract) is removed and replaced with a new artificial implant lens. This new "toric" lens has the power to correct all focusing errors.
A cornea with astigmatism has the surface shape of a football - smooth, but more round in one direction that the other. This DIFFERENCE in roundness is astigmatism. The difference causes one part of the cornea to focus light rays differently that the other resulting in TWO focus points. 
Incisional refractive surgery - Corrects astigmatism by changing the physical shape of the cornea with 2 small incisions which allow the surface to become spherical through an "unwinding" or "relaxation" of tissue tension. The procedure is called AK or arcuate keratectomy. Using the previous lens formula example, the -1.00 -2.00 x 90 could be changed to a simple myopia prescription of -1.00. This myopia could further be treated with simple glasses, simple contacts, LASIK, or a vision implant.
