what does cyl mean for glasses

In the context of glasses, CYL stands for cylinder, which represents the amount of lens power needed to correct astigmatism. It 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 cylinder column may be preceded with a minus sign (for the correction of nearsighted astigmatism) or a plus sign (for farsighted astigmatism). Cylinder power always follows sphere power in an eyeglass prescription.