SPH (sphere)
A + in the box indicates that you are long-sighted which means you find it difficult to see things close to you. A – shows that you find it hard to see things that are far away without glasses. The number might be very small, like 0.25, or a large number, like 6.00. The higher the number, the stronger the prescription lenses required. This can influence your choice of frames. The higher the prescription, the greater the curve of the lens needed.
CYL (cylinder)
The amount of astigmatism (visual distortion) that is caused by an irregularly shaped cornea. An empty box means there is no astigmatism and your eyes are perfectly spherical. A low number like 0.25 means your eyes are not quite round and a higher number like 3.00 means your eyes are quite oval.
AXIS
The direction of the astigmatism, measured in degrees. This is more for the lab to know how to position your lenses.
PRISM
This usually indicates that your eyes do not work well as a pair. Prism lenses will provide the correction you need and help prevent double vision or headaches.
BASE
The base simply tells the lab where to put the prism in your glasses.
ADD
If you require glasses for near visual work, such as reading, then you may have a number here. This is your reading addition and relates to the amount of additional correction needed to focus at close distances. A measurement will mean you have different prescriptions for distance and reading.
Int ADD
If you require glasses for visual work that is in between near and far, such as computer work, you may have an Intermediate ADD number.
