The excimer laser can be used to reduce astigmatism when performing LASIK or PRK surgery. The degree of astigmatism currently approved for correction is 0.75 D to 4.0 D. Astigmatism measurements describe to what degree the cornea is "non-spherical". As an example, the surface of a basketball is spherical and would have no astigmatism. The surface of a football, on the otherhand, would be highly non-spherical and would have high astigmatism. The excimer laser reduces the degree of astigmatism by removing corneal tissue in an asymetric manner. This is accomplished by utilizing an oval-shaped laser beam.
Astigmatic Keratotomy (AK) is a surgical procedure used to decrease astigmatism. This procedure can be used in combination with radial keratotomy and excimer laser vision correction. During astigmatic keratotomy, a diamond blade set to a precise depth makes a circumferential incision in the cornea. The incision causes the cornea to assume a more spherical shape and decreases the degree of astigmatism.