1. First things first, if you’ve got your glasses prescription in your hand – DROP IT. Your glasses prescription cannot be used to purchase contact lenses. A contact lens sits on the surface of the eye whereas a spectacle lens sits slightly further away. This difference in position affects the resulting power of the lens, and your optician needs to prescribe you contact lenses separately to glasses. Phew, glad we got that sorted.

2. Grab your paper prescription (or turn your contact lens box on it’s side, all the key information has been typed on this too).

3. Find the part that says ‘Base Curve (BC)’. This number tells you how curved your contact lens is and should look something like this: BC 8.4. To find the best fitted contact lens for you, your optician will try and match the curve of your contact lens to the curve of your eye.

4. Find the part that says ‘Diameter’. This basically refers to the size of the contact lens, and it ensures that the lens appropriately covers the correct parts of your eye. It should look something like this: DIA 13.8.

5. Find the part that says ‘Power (pwr) / Sphere (sph) / Dioptre (D)’. This refers to the power of the lens needed to correct your long or short-sightedness. If you’re short sighted, you’ll see a minus (-) sign, whereas if you are long-sighted you’ll see a plus (+) sign. The higher the number, the stronger your prescription.

6. Most contact lens prescriptions will have a brand/type/manufacturer name included, so that it is possible to reorder your lenses (provided the prescription is still valid).

7. Find the part that says ‘Cylinder’. This refers to the amount of astigmatism you have, so for some people this might be left empty. Astigmatism is to do with how curved the structures in your eye are. If you do have astigmatism, a value will be entered in this box along with an Axis. It will look something like this… Left eye: -2.25, Right eye: -2.25.

8. Find the part that says ‘Axis’. Again, this is only for those with astigmatism, so for some people this might be left empty. It is measured in degrees and this value is normally between 0-180. It is the direction where an extra power is added in the contact lens to correct your astigmatism. E.g. 10.

9. Find the part that says ‘Additional power’. This is the magnifying power which is added to your multifocal contact lenses, in order to help with close work such as reading. It can be recorded as High, Low, Medium or with the power value itself and will always be a + value. E.g. ADD LOW.

10. Remember, a contact lens prescription is not the same as a glasses prescription.