How to read your glasses prescription
A glasses prescription lists the lens power for each eye. OD is your right eye and OS is your left. SPH is the main lens power: minus numbers correct short-sightedness and plus numbers correct long-sightedness. CYL and AXIS correct astigmatism, ADD is extra power for reading, and PD is the distance between your pupils in millimetres.
The abbreviations
- OD (oculus dexter): your right eye. Sometimes written as R.
- OS (oculus sinister): your left eye. Sometimes written as L.
- OU (oculus uterque): both eyes.
- SPH (sphere): the main lens power in dioptres. A minus sign (for example -1.25) means short-sighted, so distant things look blurry. A plus sign (+1.50) means long-sighted.
- CYL (cylinder): extra power to correct astigmatism. If it is blank, you do not need astigmatism correction.
- AXIS: a number from 0 to 180 that shows the direction of the astigmatism correction. It only appears when there is a CYL value.
- ADD: extra magnifying power added to the bottom of the lens for reading, used in reading glasses and varifocals.
- PRISM and BASE: correct eye alignment. Most prescriptions do not include them.
- PD (pupillary distance): the distance between the centres of your pupils in millimetres, for example 63. Sometimes it is written as two numbers, one per eye, such as 31.5/31.5.
An example
| Eye | SPH | CYL | AXIS | ADD |
|---|---|---|---|---|
| OD (right) | -1.25 | -0.50 | 90 | |
| OS (left) | -1.00 |
This person is mildly short-sighted in both eyes, with a small amount of astigmatism in the right eye. There is no ADD, so they do not need reading power.
Glasses and contact lens prescriptions are different
A contact lens prescription includes extra measurements and the numbers can differ. Use your glasses prescription when ordering glasses.
How old can a prescription be?
Eyes change over time. Many eye care professionals recommend a new eye test every one to two years, or sooner if your vision changes. If your prescription is old, consider a new test before ordering.
How to send your prescription to Lens & Co
Go to our Prescription page, upload a clear photo or PDF of your prescription, choose your lens (Clear Lens, Anti Blue Light, Photochromic or Photochromic Blue Cut) and your frame, then send the details on WhatsApp. We confirm everything before you pay, and your lenses are made through our partner opticians.
This guide explains common terms. It is not medical advice. For questions about your eyes, speak to a qualified optometrist or ophthalmologist.
Frequently asked questions
What does a minus number on my prescription mean?
A minus SPH number means you are short-sighted: you see near things clearly and distant things look blurry. The bigger the number, the stronger the lens.
What if my prescription does not show my PD?
Ask the clinic that tested your eyes, or tell us on WhatsApp when you order and we will guide you.
Can I add a blue light filter to my prescription lenses?
Yes. Choose Anti Blue Light or Photochromic Blue Cut when you upload your prescription.
