SPH (sphere) - the amount of long (+) or short (-) sight. The higher the number, the stronger the prescription lens required.
CYL (cylinder) - the amount of astigmatism, or visual distortion, caused by an irregularly shaped cornea.
AXIS - the direction of the astigmatism, measured in degrees.
PRISM - correction needed to balance the eyes.
ADD - the amount of additional correction needed to focus at close distances. If you have a measurement shown in this section we advise that you order these lenses in store. It means that you have different prescription requirements for distance and reading. This can be solved by having different spectacles, or bifocal or varifocal lenses.

PD To ensure your comfort and optimum vision we require one measurement, this is called your PD (Pupillary Distance). This may be written on your prescription, if so select it from the PD menu.
If there is no note on your prescription do not worry. You can measure this by placing your face about 20cm (8inches) away from a mirror. Placing a ruler on your forehead and measuring between the centres of your pupils (the black part) of your eyes. (milimetres)
We will use these measurements to make you the best possible spectacles.