Understanding your prescription
What your prescription really means
Ever wondered what all the symbols and numbers on your prescription mean?
‘+’ or ‘-‘
‘+’ – Shows if you are long sighted (longsightedness)
‘-‘ – Shows if you are short sighted (shortsightedness)
PD
PD – Pupillary distance is the distance between your eyes measured between your pupil centre points
SPH
SPH – Spherical number shows how strong the correction needs to be
CYL
CYL – Cylinder number shows how much astigmatism you have
AXIS
AXIS – Axis shows the position of the cylinder and will be between 1 & 180
PRISM
PRISM – This shows if you have a muscle imbalance in your eye
BASE
BASE – This shows the direction of the prism in your lens
ADD
ADD – This will indicate if you need a prescription for reading. Is applied to bifocal and varifocal lenses to correct presbyopia
You can read more about different types of prescriptions here.
Common layouts of prescriptions
Below are examples of prescriptions. The first set are standard prescriptions. Look through these to get a feel. Typed prescriptions are generally quite easy to understand, it’s mostly handwritten ones that cause problems.
At the end of the page are examples of unusual cases you may encounter, with instructions for what to do. Skip straight to the more unusual items.
This is a standard NHS prescription:
It would be written as follows:
Dolland & Aitchinson
- This time the signs have been written ABOVE the numbers - they are still just standard +/- signs
- Also, they optician has written 125 instead of 1.25. It should still be entered as ‘1.25’ with a decimal point.
- There is only one value for Near ADD, this should be entered for both eyes.
It would be written as follows:
Specsavers
It would be written as follows:
Vision express
Here the additions are placed away from the rest of the prescription, it would be written as follows:
More unusual figures
Sometimes figures like this appear on your prescription. These are not needed to make your lenses.
Some prescriptions have this figure, which looks like a sideways 8. This means ‘infinity’. And you should select ‘infinity’ from the list.
This prescription also has some figures scrawled underneath these are Additions for both intermediate and near distances. Even though it’s a single figure, it applies to both eyes.
This would be written like this: NOTE: Use the “My prescription is more complex than this…” link to show you this more advanced prescription area
Sometimes opticians write ‘DS’ in the CYL column. This simply means there is no astigmatism, and you can enter either nothing (leave the field blank) or select the phrase DS in the drop down.
