Understanding Prescriptions

How many times have we looked at the prescription given to us at the end of a sight test and not understood what is written down in front of us. Imagine what it must be like for some of your clients.

Please see below a description of all elements found on a NHS certified prescription form.

At Sightcall we go above and beyond to ensure we are as clear as possible with the information provided to your clients. However understanding a little  bit about the details found on a prescription can help you to explain to your clients what is happening with their sight and help to put minds at ease at any time.

Caring doesn’t stop with office hours…..

SPH (sphere)

A plus sign in front of the number means you are long-sighted (difficulty focusing on close objects). A minus sign means you are short-sighted (difficulty focusing on distant objects) the number will indicate the strength of lens: the higher the number, the stronger the prescription lenses required.

CYL (cylinder)

This number indicates the amount of astigmatism you have (how the eye focuses light based to the shape of your cornea). If this box is empty, it means that there is no astigmatism and your eyes are perfectly spherical, like a ball. As the number increases, it indicates that’s your eyes are more oval in shape.


This is to help your eyes work together more effectively as sometimes one or both eyes may tend to pull up, down, to the right or to the left. A prism in the lenses will help move the image into place so the brain sees only one imagine.


This indicates the rotation of the prism to enable the glazing technician to know which position your lenses should be in the frame.


From the age of 40+ you may start to notice that you require additional correction to focus at close distance, This number will be used to create reading glasses, or for the bottom half of your bifocals or varifocal lenses.