Understanding Your Prescription

It could be your first prescription, or you could be a seasoned spectacle wearer, either way the numbers on your script can sometimes be confusing. We hear a lot of people say "How do I know what my glasses prescription means?".

Understanding your prescription can in turn help you with choosing the right spectacles. 

This simple guide is designed to make the numbers on your prescription make sense, so you know exactly what you want and need to order. 

One important thing to take note of is that your spectacle prescription is different to your contact lens prescription. Never order glasses using a contact lens prescription as it will affect your vision. 

Your prescription is often noted in a table format, which can vary dependent on the optician or country you have had your eye test at, see our examples below.

Sph: The sphere measurement is the power of your lens which indicates the degree of long or short sightedness. If you see a plus sign + in front of the numbers you are longsighted, but if you see a minus sign - in front of the numbers you are shortsighted.  

Cyl: The cylindrical value relates to the astigmatism, which measures the deviations in the curvature of your eyeball. The optician may have said your eyes are more shaped like a rugby ball if you have astigmatism. 

Axis: The axis works in partnership with the Cyl, you can't have one without the other.  The axis is the angle at which the Cyl power needs to be positioned and can vary from 1 to 180 degrees. This number has no bearing on the strength of your prescription.

Prism & Base: Prism is added to a prescription when you have a muscle weakness in the eye. The base tells of the direction the prism needs to be facing. Prism can be in one or both eyes and can vary in direction depending on the type of prism required. 

Near Add: The near add indicates how much additional power you need for reading and close work. 

Int Add: The Inter add refers to your intermediate vision and how much additional power you need to see things at middle distance. You may or may not have this noted on your script. It is often found on those who spend time on desktop computers, or someone who has a particular need or hobby, such as reading sheet music off a stand. 

We hope this little guide helps you understand your glasses prescription in more detail. If you still have questions or queries, then remember we are just an email away info@retrospectacle.co.uk