Understanding Your Prescription

I think the most common question we get asked, apart from "do you sell colour lenses?", is "how do you make sense of your prescription?" You've finally got the golden ticket, and you're ready to rush home to pick up your trial lenses from behopi.com but you look down at the slip from the test & it looks like it's all written in language created by J.R.R Tolkien

However, unless you're a trained optometrist or just general all round know it all, a prescription can be confusing AF! I hear you, "What does CYL mean?" "What numbers do I need to choose on the website?" That's why we've created this short 10 step guide to help you navigate your new prescription! We'll let you know what to look out for and make signing up to Hopi, that bit easier!



  1. First up, don't assume your lens prescription will be the same as your glasses. We advise all our customers to get correctly fitted for lenses. Your glasses normally sit up to an inch in front of your eyes, compared to a lens which sits directly on the surface. That can cause a difference between the power needed in your glasses, compared to your lenses
  2. This is typically what your prescription looks like. In the UAE, you'll either get a small card or piece of paper with all your details in and sometimes they optician just writes it down for you
  3. Look for initials 'BC' - this stands for Base Curve. 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 & match the curve of your contact lens to the curve of your eye
  4. Find the part that says ‘Diameter (DIA)'. 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) - normally in the UAE this isn't the case and you're free to try any lenses you want to. We're hoping you chose Hopi of course!
  7. Find the part that says ‘Cylinder (CYL)'. 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: -1.25, Right eye: -1.25
  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. We've done a good job of explaining everything on there but if you're still hesitant, just drop us a note at hello@behopi.com and we'll help you out

For our website, you'll need the 'Power' or 'Sphere' data to input on the left eye & right eye. Sadly we don't have toric lenses if you have an astigmatism but if you have a minor cylindrical (cyl) value of 0.50 or less, it might be worth giving our lenses a try! Want to start your 30 day trial with Hopi? Sign up here