SPH (Sphere)
Lens strength needed to correct your vision. Negative (-) means nearsighted, Positive (+) means farsighted.
CYL (Cylinder) & Axis
The degree of astigmatism in your eyes, as well as an axis number that indicates the orientation of the astigmatism.
ADD (Addition)
ADD stands for the additional correction that you need for reading. It's used for multifocal lenses and readers.
Prism
Prism is used to correct diplopia (double vision). A prism bends light to align your vision so only a single image is seen.
Vertical Prism
Vertical prism correction is for vertical eye misalignments & prescribed upwards in one eye and downwards in the other.
Horizontal Prism
Horizontal prism correction is for lateral eye misalignments & prescribed in the same direction for both eyes.
