If you’ve ever looked at your glasses prescription and wondered whether you can use the same details to buy contact lenses, you’re not alone. It’s one of the most common questions asked by people switching between glasses and contact lenses.
The short answer? No – a contact lens prescription is not the same as a glasses prescription.
Here’s why, and what you need to know before ordering lenses.
Why Contact Lens Prescriptions Are Different
Although both prescriptions correct your vision, glasses and contact lenses sit in very different positions on your eye.
Glasses sit around 10–14mm away from your eyes
Contact lenses sit directly on the surface of your eye
That small difference in distance means your prescription needs to be adjusted to ensure your vision is clear and comfortable when wearing contact lenses.
What’s Included in a Glasses Prescription?
A glasses prescription typically includes:
SPH (Sphere): how short- or long-sighted you are
CYL (Cylinder) & AXIS: correction for astigmatism
ADD: reading strength for varifocals or bifocals
PD (Pupillary Distance): used for lens positioning in frames
This information is perfect for making spectacle lenses — but it’s not enough for contact lenses.
What’s Included in a Contact Lens Prescription?
A contact lens prescription includes everything needed to ensure the lens fits your eye safely and comfortably:
Base Curve (BC): the curvature of the lens
Diameter (DIA): the size of the lens
Brand and lens type: not all lenses fit the same
Power adjustments: fine-tuned for lens position on the eye
These measurements can only be determined through a contact lens fitting, carried out by an optician or optometrist.
Can You Convert a Glasses Prescription into Contact Lenses?
It might be tempting to try converting a glasses prescription yourself, especially if the numbers look similar, but this isn’t recommended.
While opticians can mathematically adjust prescriptions (especially for stronger powers), fit and eye health still matter. Wearing contact lenses that don’t fit correctly can lead to:
Eye irritation or dryness
Blurred or fluctuating vision
Increased risk of eye infections
That’s why a valid contact lens prescription is always required.
Do You Need Separate Eye Tests?
Yes, and for good reason.
Eye test: checks your vision and eye health
Contact lens fitting: checks how lenses sit, move, and feel on your eyes
Even if your glasses prescription is up to date, you’ll still need a contact lens fitting before ordering lenses.
Can Your Glasses Prescription Change When Wearing Contacts?
Sometimes, yes.
Because contact lenses sit directly on the eye, your optician may slightly adjust the strength, especially if you have a stronger prescription or astigmatism.
That’s completely normal and helps ensure your vision is as sharp as possible.
Where Does My Glasses Reglaze Fit In?
At My Glasses Reglaze, we specialise in restoring and upgrading your spectacle lenses, not contact lenses.
If you already have a valid glasses prescription, we can help you:
Replace scratched or damaged lenses
Upgrade to anti-glare, blue-light or thinner lenses
Give your favourite frames a whole new lease of life
Just remember: contact lenses always require their own prescription and fitting from an optician.
Using The Correct Prescription For Clearer Vision
While glasses and contact lenses both correct your vision, they are not interchangeable. Using the correct prescription ensures clearer vision, better comfort, and healthier eyes.
If you’re unsure which prescription you have or need new lenses for your glasses, My Glasses Reglaze is here to help.
