SPH (Sphere) indicates the level of lens power prescribed for nearsighted or farsighted vision. It''s measured in diopter and uses plus (+) for farsightedness (hyperopia) and minus (-) for nearsightedness (myopia).

Plano/PL indicates that the SPH is zero. If you don''t see numbers for CYL and AXIS, the lenses don''t correct for refractive error and might be for UV protection, blue light filtering, or just for fashion.

CYL (Cylinder) & Axis numbers (between 0 and 180 degrees) are required to correct astigmatism. Look out for both, as you''ll need CYL and Axis together.

SPH/DS If SPH or DS is written in the CYL section of your prescription, it means no astigmatism is present. Enter ''0'' in the CYL section of your prescription form.

ADD (Addition) indicates correction is needed for near vision, in the form of multifocal or reading glasses. If you see one number listed for ADD, use it for both eyes.

Prism is used to help correct diplopia, or double vision. The prism bends light to help align the vision so only a single image is seen. We don''t currently provide prescription glasses with prism correction.

Visual Acuity refers to your ability to clearly see shapes and details of the things around you. It''s just one factor in your overall vision. Visual Acuity is not needed to fill out our prescription form.

Prada Eyewear