How to Read Your Glasses Prescription: A Simple Guide

Ordering prescription glasses online can feel like trying to solve a puzzle in a different language. We get it! It’s all SPH, CYL, and numbers that seem to come from a math textbook.

But here’s the secret: it’s actually really simple once you know what’s what. This guide breaks down exactly what your optician has written, so you can choose the perfect lenses for your eyes with 100% confidence.

Your Prescription Explained

Your glasses prescription is basically the formula for your perfect vision. It tells us how to make lenses that match your eyes — whether you need help with distance, reading, or both.

1. SPH (Sphere): Your Main Strength

  • A minus (–) means you’re nearsighted

  • A plus (+) means you’re farsighted This is the part most people recognise—your main lens strength.

Top Tip: If your SPH number is higher than +/- 4.00, check out our High-Index Lenses guide to see how we keep your lenses looking thin and sleek.

2. CYL + AXIS: Astigmatism (If You Have It) If your prescription includes CYL and AXIS, it simply means your eye has a slightly different shape and needs a little extra correction.

  • CYL = the amount

  • AXIS = the direction. If these boxes are blank, you don’t have astigmatism. Our UK-based optical lab handles precision astigmatism cuts every single day, so you're in safe hands.

3. ADD: Extra Help for Reading If you wear varifocals, bifocals, or reading glasses, you’ll see an ADD number. This gives you that close-up “boost” for reading or screen work. This is the magic number we use when crafting your progressive or varifocal lenses.

4. PRISM: Less Common If PRISM is on your prescription, your optician is correcting eye alignment or double vision. Most people won’t have this.

5. PD (Pupillary Distance) Your PD tells us how far apart your eyes are. We need this to make sure your lenses sit perfectly in the frame. If it isn’t written on your prescription (which is common!), you can use our free PD Calculator or just ask us for help.

FAQs:

Can I use my NHS prescription to order glasses online? Absolutely! Just upload your prescription at checkout, or email it to us if you have questions.

What if my prescription is over a year old? It’s best to have an up-to-date prescription (within the last 2 years) for accuracy and comfort.

What if I don’t know my PD? No worries! We have a free PD Calculator or you can ask your optician.

Do you offer help choosing frames for strong prescriptions? Yes! Our team can recommend styles that suit any prescription strength and keep you looking great.

Ready to Order? Shop with Confidence!

Browse our collection of stylish, affordable frames here: Mens, Womens, or Unisex, and simply upload your prescription at checkout.

Still stuck? Don't worry-drop us a message and we’ll help you decode your prescription, no magnifying glass required!

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