what is cyl in eye prescription

In an eye prescription, "CYL" stands for cylinder, and it represents the amount of lens power needed to correct astigmatism, if present. Astigmatism is a condition in which the cornea has a different curve, causing distorted vision at both near and far distances. The CYL value indicates the difference in the greatest and weakest powers of the eye, usually separated by 90 degrees. If there is no value in the CYL column, it means that either there is no astigmatism, or the astigmatism is so slight that it does not need to be corrected with eyeglass lenses. The CYL value may be preceded by a plus or minus sign, and it typically ranges from +/-0.25 to +/-4.00.