The Sphere (SPH)
The sphere or SPH number on your prescription indicates the amount of lens power needed (prescribed) to correct your vision. The number has a minus sign (–) to correct short sightednessor a plus sign (+) to correct long sightedness. The higher the number the stronger the lens needed.
The term "sphere" means that the correction is spherical or equal across the eye.
The Cylinder (CYL)
The Cylinder or CYL number on your prescription indicates the amount of correction to remove any visual distortion, caused by an irregularly shaped cornea known as an astigmatism. If there isn't a number you either don't have an astigmatism or it is very slight.
The Axis measurement is used in your prescription to ensure that the CYL is correctly positioned. It is given in degrees from 1 to 180.
The ADD (Addition)
The ADD Inter is the amount of correction needed on your prescription for you to cope with intermediate distances, such as working at a computer or reading music.
ADD Near is the amount of correction needed on your distance prescription so you can see near objects clearly, such as reading a book or map.
A Prism is not commonly prescribed on an optical prescription. Occasionally it is prescribed to correct a crossed-eye (strabismus) or other eye muscle /focusing disorder.
PD / Pupillary Distance
The pupillary distance (PD) is the distance between the centers of the two pupils between the eyes. This measurement is essential to ensure glasses are comfortable to wear and provide correct vision.