Your eye prescription is the written result of your eye exam. It is a short set of numbers that tells an optician exactly how to make lenses that give you clear, comfortable vision. If you have never understood what those numbers mean, you are not alone — most people only learn about them when they order glasses online.
What a prescription actually is
During an eye exam, an optometrist tests each eye separately to find the lens power that gives you the clearest sight. The results are written on your prescription, usually with one row for your right eye (OD) and one for your left eye (OS). The prescription also has an expiry date — most are valid for one to two years, and many optometrists recommend having your eyes checked at least every two years, or sooner if your vision changes.
What your prescription says about your vision
The values on a prescription describe common focusing problems:
- Nearsightedness (myopia): distant objects look blurry while near objects stay clear. Your SPH value will be negative, for example -2.50.
- Farsightedness (hyperopia): near objects are harder to see clearly. Your SPH value will be positive, for example +1.75.
- Astigmatism: the front of the eye is shaped more like a rugby ball than a football, so vision can be blurred at all distances. This is shown by the CYL and AXIS values.
- Presbyopia: the gradual loss of near focusing that usually starts in your 40s. It is corrected with the ADD value, which is added to your distance prescription for reading.
These are common, correctable conditions. A prescription does not measure how healthy your eyes are — that is what the rest of the eye exam is for.
Distance, reading — or both?
Some people need glasses only for distance, and others only for reading. Many people need both, and that is where lens choice matters: single vision lenses correct one distance, while progressive lenses blend distance, intermediate and reading zones into one lens with no visible line. Which one suits you depends on your prescription and how you use your glasses day to day.
Do not forget your PD
Your pupillary distance (PD) is the distance between the centres of your pupils, measured in millimetres — usually between 54 and 70. It is not always printed on a prescription, but it is essential for making glasses: the optical centre of each lens must sit in front of your pupil. FrameAura asks for your PD when you order prescription glasses, and our checkout also lets you upload your prescription so we can check it before your lenses are made.
When to get your eyes checked again
- You notice your vision is less clear than it was.
- You get headaches, eye strain or tired eyes after reading or screen work.
- You squint, or you hold books and your phone closer or further away.
- Your last eye exam was more than two years ago.
Children should have their eyes checked regularly too — many vision problems are easier to manage when they are found early.
Ordering glasses with your prescription at FrameAura
When you order prescription eyeglasses with us, you can upload a clear photo or scan of your prescription, or type the values in yourself — right eye (OD) and left eye (OS) SPH, CYL, Axis and ADD, plus your PD. We check every prescription before your lenses are cut, and if anything is unclear we contact you. If the numbers on your prescription still look confusing, our guide How to Read Your Glasses Prescription explains each one line by line.
This article is general information only and is not medical advice. If you have concerns about your eyesight, see an optometrist or eye care professional.