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 amount of astigmatism (visual distortion) that is caused by an irregularly shaped cornea. If this box is empty, it means that 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.
The direction of the astigmatism, measured in degrees. This number is more for the lab as it helps them to know how to position your lenses.
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.
The base simply tells the lab where to put the prism in your glasses.
ADD - If you are over 40, 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. If a measurement is shown in this section, it means you have different prescriptions for distance and reading. Bifocal or varifocal lenses may be needed. Sometimes another add for intermediate prescriptions is also required.
In some cases the near add is written on the prescription in a different format and is already combined to provide the near prescription.
If you have any questions about your prescription or would like a copy of your prescription please contact your local store, or the store where you had your eye test.