Reading a contact lens prescription can feel confusing at first. Numbers, abbreviations, and symbols don’t always make it obvious what they mean — but once you understand the basics, ordering contact lenses online becomes quick and easy.
This guide explains each part of a contact lens prescription in simple terms, so you can confidently choose the right lenses for your eyes.
Is a Contact Lens Prescription Different from a Glasses Prescription?
Yes — and this is very important.
A contact lens prescription is different from a glasses prescription. Contact lenses sit directly on the eye, so they require additional measurements to ensure proper fit, comfort, and eye health. You should always use a contact lens prescription when ordering lenses online.
👉 If you’re not sure which lenses suit you, see our guide: How to Choose Contact Lenses
The Main Parts of a Contact Lens Prescription
A typical prescription includes the following values for each eye.
SPH (Sphere)
SPH indicates the strength of the lens needed to correct short-sightedness (myopia) or long-sightedness (hyperopia).
A minus (-) value means you are short-sighted
A plus (+) value means you are long-sighted
Example:SPH -2.50 or SPH +1.75
Most people only need this value if they do not have astigmatism.
👉 Shop lenses by power in Daily Contact Lenses or Monthly Contact Lenses
BC (Base Curve)
Base Curve describes how curved the lens is. It helps ensure the lens fits comfortably on your eye.
Example:BC 8.6
Not all brands offer multiple base curves, so it’s important to choose lenses that match your prescription.
DIA (Diameter)
Diameter is the size of the lens from edge to edge, measured in millimetres.
Example:DIA 14.2
Like BC, this value affects comfort and stability on the eye.
CYL (Cylinder) and AXIS
These values appear if you have astigmatism.
CYL shows how much correction is needed
AXIS shows the orientation of the correction (from 0° to 180°)
Example:CYL -1.25AXIS 90
If your prescription includes CYL and AXIS, you need toric contact lenses.
👉 Browse options in Contact Lenses for Astigmatism (Toric)
ADD (Addition)
ADD is used for multifocal contact lenses and helps with near vision, such as reading.
It is usually written as:
LOW
MED
HIGH
or as a numeric value (e.g. +1.50)
If your prescription includes ADD, you will need multifocal lenses.
👉 Explore Multifocal Contact Lenses
Do Left and Right Eye Prescriptions Differ?
Very often, yes. Many people have different prescriptions for each eye.
When ordering online, make sure you enter the correct values for:
Left eye (OS)
Right eye (OD)
Never assume both eyes use the same prescription unless your eye care professional has confirmed it.
How Often Should You Update Your Prescription?
Most eye care professionals recommend a contact lens check every 12–24 months. Your vision, eye shape, or tear quality can change over time, even if your eyesight feels the same.
Wearing outdated lenses may cause discomfort, dryness, or blurred vision.
What If You’re Unsure About Your Prescription?
If anything on your prescription is unclear, it’s best to check with your optician before ordering. Guessing values or using an old prescription can put your eye health at risk.
For first-time wearers, start with our guide: How to Choose Contact Lenses
Final Thoughts
Understanding your contact lens prescription makes buying lenses online simple and stress-free. Once you know what each value means, you can confidently select lenses that provide clear vision, comfort, and safety.
At WeLoveLenses, we make it easy to enter your prescription correctly and find lenses that suit your needs.
