SPH (Sphere)
Spherical error, or overall power of lens is the basic part of your prescription. A (+) means you have trouble seeing near, and a (-) means you have trouble seeing things faraway.
CYL (Cylinder) & Axis
A cylinder value indicates astigmatisms or perpetually blurry vision. Axis—measured between 1 and 180°— tell us the orientation of the astigmatism
ADD (Addition)
This number is sometimes written NV for near vision and is used for multifocal lenses and readers
PRISM
We can process prism prescriptions to correct eye orientation
Vertical Prism is used to help correct vertical eye misalignments and is prescribed in opposite directions for both eyes
Horizontal Prism is used to help correct lateral eye misalignments and is always prescribed in the same direction for both eyes
