How to Read Eye Prescription

OD=right eye OS=left eye OU=both eyes


SPH(Sphere/Spherical): This indicates the amount of lens power, prescribed to correct nearsightedness or farsightedness. If the number appearing under this heading has a minus sign (–), you are nearsighted; if the number has a plus sign (+) or is not preceded by a plus sign or a minus sign, you are farsighted. The larger the number following the +/-, the stronger the prescription.

CYL(Cylinder/Cylindrical): This indicates the amount of lens power for astigmatism. This number also has "+" or "-" signs. If "DS" or "SPH" or "spherical" or "PL" is stated under CYL, it means you have no astigmatism.

Axis: This number indicates the orientation of your astigmatism and is measured in degrees. It will be between 1 and 180. If an eyeglass prescription includes cylinder power, it must also include an axis value, which follows the cylinder power.

Add: ADD is an additional strength for your lens for reading or upclose work. If you need reading, intermediate, bifocal or multifocal, or progressive lenses, this should be listed in your prescription. Just have one ADD number on my prescription? That’s because for most people, ADD will be the same for both eyes. It is typically the same positive number, for both eyes, although it may be written only once on your prescription. It may also be written as a large, positive number, across both the OD and OS lines of your prescription.

PD: Pupillary Distance is the distance between your pupils in millimeters. Your PD is very important for accurately fitting your lenses to achieve visual acuity.

Prism: refers to the prismatic power used to correct vision displacement. It helps to correct some special conditions or some eye disorders (like squints) that require the focused image to move position. The measurement is Prism Dioptre. The value may be as high as 10 and may go up in steps of ½ or 1 Prism Dioptre's.

PL: Plano. Latin for "flat." If this is in the SPH section of an Rx, it means no nearsighted or farsighted correction is needed.