How to read your eyeglasses prescription

SPH, CYL, AXIS, ADD and PD explained in plain language.

SPH (sphere) is the lens power for near or far sight. CYL (cylinder) and AXIS describe astigmatism. ADD is the extra magnification for reading, used in progressives. PD (pupillary distance) is the distance between your pupils, needed to center the lenses. A minus sign means nearsighted, a plus sign means farsighted.