Getting your eye prescription can feel like decoding a secret message. This guide puts the pieces in the right order so you can quickly answer: what does my eye prescription mean, what each abbreviation (SPH, CYL, Axis, PD, BVD, Near Add, etc.) actually does, and how to use the information when ordering glasses online.
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What does my eye prescription mean?
Your prescription is a set of measurements from your optician that tells us how to make lenses to correct each eye. Read each eye’s line (labelled OD for right and OS for left) left-to-right: you’ll usually see distance power (SPH), astigmatism (CYL + Axis), additions for near (ADD), and sometimes alignment or fitting metrics (Prism, PD, BVD).
OD / OS / OU — which eye is which?
OD = Oculus Dexter = right eye. OS = Oculus Sinister = left eye. OU = Oculus Uterque = both eyes. Always check which column/line corresponds to OD and OS before sending us your prescription for glasses or reglazing.
What is SPH (Sphere)?
SPH (Sphere) is the main power used to correct short-sightedness or long-sightedness.
- Negative value (−) = myopia (short-sighted), e.g.
-2.00 - Positive value (+) = hyperopia (long-sighted), e.g.
+1.50
Higher absolute numbers mean a stronger prescription.
CYL and Axis
What is CYL?
CYL (Cylinder) corrects astigmatism, where the eye’s shape is slightly elliptical rather than perfectly round. The CYL number shows how much correction is needed.
What is Axis?
Axis is a number from 1 to 180 showing the orientation of the cylinder correction on the lens. CYL and Axis always go together. Example: SPH -2.00 CYL -1.00 AXIS 090.
Prism — when it appears on a prescription
Prism correction helps with eye alignment problems, such as double vision, and is measured in prism dioptres with a base direction (up, down, in, out). Please provide the prism details exactly as written when sending your prescription to us so we can create accurate lenses.
What is Near Add and Intermediate Add?
Near Add (ADD) is extra magnifying power added for reading or close work — used in bifocals, varifocals, and reading glasses. Example: ADD +1.75.
Intermediate Add (Inter Add) may appear for mid-distance tasks like computer use. Multifocal lenses provide zones for distance → intermediate → near vision.
What is PD (pupillary distance)?
PD is the distance between your pupils in millimetres. Accurate PD ensures the optical centres of your lenses align with your eyes, giving you clear and comfortable vision. If you’re unsure of your PD, we can guide you on measuring it.
What is BVD (back vertex distance)?
BVD measures the distance from the back surface of the lens to your eye. This is especially important for high prescriptions, as small changes can affect lens power. Please provide BVD if it is noted on your prescription.
Notation & format: plus vs minus cylinder, BAL, common layout
- Plus vs minus cylinder: Some opticians use +CYL notation, others −CYL. We can convert between formats to create the correct lenses.
- BAL = Balance — used when one eye has no measurable correction; the other lens is adjusted for comfort.
- Typical layout per eye:
SPH / CYL / AXISfollowed by optionalADD,PRISM,PD,BVD.
Sample prescription — read this line
OD: -2.00 / -1.00 x 090 ADD +1.75 PD 62 BVD 12mm
How to read it:
- OD (right eye)
- SPH -2.00 → distance myopia
- CYL -1.00 at Axis 090 → astigmatism correction
- ADD +1.75 → near reading power
- PD 62 → pupillary distance
- BVD 12mm → back vertex distance for accurate lens power
Order Your New Lenses
Understanding the order and relationship between SPH → CYL+Axis → ADD → PD → BVD makes reading a prescription fast and reliable. If you’re ready to reuse favourite frames, send them and your current prescription and we’ll fit them with precise new lenses.
Frequently Asked Questions About Varifocal Glasses
How long does a prescription last?
In the UK: typically 2 years for adults, but this can vary:
Children: often 1 year (or sooner, depending on growth and needs)
People with certain eye health issues: more frequent checks recommended
Always check the date on your prescription, opticians may stamp a recommended review period.
Can I use an old prescription to order glasses?
It’s not recommended if your prescription is out of date. Always ensure your prescription is current before ordering new lenses through our service.
What if my prescription format looks different?
Prescriptions may be written in plus or minus cylinder formats, or laid out differently depending on your optician. We can convert between formats to make sure your lenses are made correctly.
Do I need PD to order online?
Yes, we usually require your pupillary distance (PD) to ensure lenses are correctly centred for comfortable vision. If you don’t have it, we can guide you on how to measure it or accept an optician-measured PD.
Can I order glasses online if I have prism in my prescription?
Prism correction requires precise alignment. We can handle prism prescriptions accurately, but it’s important to provide all details exactly as written on your prescription.
Is it safe to order multifocal or varifocal lenses online?
Yes, as long as your prescription includes all necessary measurements (distance, near, intermediate, PD, and BVD if needed). We can process these accurately and help ensure a comfortable fit.
Can I order children glasses online?
Children under 16 (or under 19 in full-time education) require in-person fittings, so online ordering is not available for them.
