A glasses prescription can look like a string of numbers and abbreviations. This simple guide explains what the main terms mean, how they relate to vision correction, and what to consider when choosing prescription glasses, reading glasses or varifocal lenses.
How to read an eyeglasses prescription
Your prescription usually has separate columns for your right eye (often marked R or RE) and left eye (L or LE). The figures can differ between your eyes. They describe the lens power and, where needed, other corrections.
- SPH or sphere
- The main lens power for short-sightedness or long-sightedness. A minus sign usually indicates short-sighted correction; a plus sign usually indicates long-sighted correction. The larger the number in either direction, the stronger the sphere power.
- CYL or cylinder
- The amount of astigmatism correction. Astigmatism can make vision blurred or distorted at different distances.
- AXIS
- A number in degrees that gives the direction of the cylinder correction. It is used with CYL and does not describe how strong the prescription is.
- ADD
- Extra near power, commonly used in reading glasses, bifocals and varifocal lenses to help with close work.
- Prism and base
- These appear on some prescriptions when a prism correction is needed to help align how the eyes work together.
PD means pupillary distance, the measurement between your pupils. It is used to position the lenses in a frame, but it may be recorded separately from the written spectacle prescription.
What is a “bad eyesight prescription”?
There is no single number that makes an eye glasses prescription “bad”. The figures show the correction needed for clearer vision; they are not a score for eye health. A strong prescription can still be corrected with suitable lenses. An eye examination also checks eye health, so a glasses prescription on its own does not tell the whole story.
Choosing prescription glasses and lenses
The right prescription glasses depend on your prescription, the frame, how you use your glasses and what feels comfortable. If you have a higher lens power, your dispensing optician can explain frame and lens options that may help with thickness, weight and appearance. Lens choice should be discussed with a qualified professional, especially for a new or complex prescription.
- Single-vision lenses correct one main viewing distance and are commonly used for distance or reading glasses.
- Varifocal lenses provide distance, intermediate and near vision in one lens, with no visible dividing line. There can be an adjustment period while you get used to looking through the different areas.
- Anti-reflective or anti-glare coating can reduce reflections from lens surfaces and may make lenses look clearer in some indoor and night-time settings.
- Photochromic lenses darken in bright light and become clearer indoors. Ask your optician how they behave in different conditions.
- Prescription sunglasses combine vision correction with sun protection. Ask about UV protection and whether polarised lenses suit how you use them.
There is no one lens that is best for everyone. If you are comparing designer prescription glasses, reading glasses or prescription sunglasses, ask what each option will do for your prescription and daily routine.
Do I need a new eye test before buying glasses?
Check the date and any expiry information on your prescription. If it is out of date, your vision has changed, or your glasses no longer feel right, arrange an eye test before ordering new lenses. In the UK, your optometrist should provide your prescription or explain if a referral is needed.
At Specialeyes Eyecare, our team can explain your spectacle prescription and talk through glasses and prescription lens options at our Shepherds Bush practice. Read more about our glasses and lens services in West London.