How to read your prescription
What does SPH mean on my glasses prescription?
The SPH on your glasses prescription stands for sphere. Sphere refers to the power of your lens (measured in dioptre units) to correct the degree of short or long sight you have. Commonly, this number will be different for each eye.
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 as the higher the prescription, the greater the curve of the lens needed.
What does CYL mean on my glasses prescription?
The abbreviation CYL on your prescription stands for cylinder. This indicates the amount of lens power required to correct any astigmatism present.
Astigmatism results from having a cornea that is not perfectly spherical. 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.
What does AXIS mean on my glasses prescription?
The axis number on your prescription tells your optician which direction they must position any cylindrical power in your lenses (required for people with astigmatism).
This number shows the orientation or angle in degrees from 1 to 180. The number 90 means vertical position and 180 horizontal. A higher number for the axis doesn’t mean that your prescription is stronger — it just describes the position of the astigmatism.
What does PRISM mean on my glasses prescription?
If you require a prismatic correction in your glasses this usually indicates that your eyes aren’t working well as a pair. Prism lenses will provide the correction you need and help prevent double vision or headaches.
What does the BASE mean on my glasses prescription?
The base simply tells the lab where to put the prism in your glasses.