In an eye prescription, CYL stands for Cylinder, which represents the amount of lens power needed to correct astigmatism. Astigmatism is a condition where the eye is shaped more like a football than a basketball, causing distortion in both near and far vision. The CYL value indicates the difference in the greatest and weakest powers of the eye, usually separated by 90 degrees. If nothing appears in this column, either you have no astigmatism, or your astigmatism is so slight that it is not necessary to correct it with your eyeglass lenses. The number in the CYL column may be preceded with a minus sign (for the correction of nearsighted astigmatism) or a plus sign (for farsighted astigmatism). The CYL power always follows the sphere power in an eyeglass prescription.