Understanding your Prescription


Prescriptions explained

A spectacle prescription is usually written in the following form:
Sphere Cylinder Axis
R -3.00 / -0.50 x 180
L -3.50 / -1.00 x 180



Your glasses prescription contains the precise measurements of the type of prescription lenses that you will need in order to have the clearest vision.
SPH (sphere)
A plus sign (+) in the box indicates that you are long sighted which means you find it difficult to see things close to you.
A minus sign (–) 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 5.00.
The higher the number, the stronger the prescription.
CYL (cylinder)
The amount of astigmatism 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, like a football. If there is a low number, like 0.25, it means that your eyes are nearly round but not quite. A higher number, like 3.00 shows that your eyes are quite oval in shape.
AXIS
The direction of the astigmatism, measured in degrees. The number is not related to how well you can see but it helps the lab know what angle to position your lenses in the frame.
PRISM
This normally indicates that your eyes do not work well as a pair. If there is muscle imbalance between your eyes, 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 are over 40, there may be a number where it says ‘ADD’. 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. 


Please Note:
The prescription you supply to us must be given to you by a registered optician or registered ophthalmic medical practitioner following a sight test performed by him or her within the last 2 years or 12 months if over 70 years of age and that you are not registered blind.