Prescription guide
Read your prescription
Your prescription is shorter than it looks: four numbers per eye and one for the space between them. Here is what each one means, in plain English.
What the numbers mean
UK prescriptions list the right eye first (R or OD), then the left (L or OS). Copy each row exactly, signs included.
SPH
Sphere
The main power of the lens, in 0.25 steps. Minus (-) corrects short sight, plus (+) corrects long sight. This is the number that matters most. We can make lenses from -20.00 to +12.00.
CYL
Cylinder
How much astigmatism correction you need, if any. Zero, blank, DS or "plano" all mean none. It is always paired with an axis. Range -6.00 to +6.00.
AXIS
Axis
The angle the cylinder sits at, from 1 to 180 degrees. Only meaningful alongside a CYL value. If you have a CYL you must have an axis.
ADD
Reading addition
The extra near power for reading glasses, bifocals or progressives. Usually only present from your 40s onwards, and usually the same for both eyes. Range +0.75 to +3.50.
PD
Pupil distance
The distance between the centres of your pupils in millimetres. It is often left off the prescription, so you may need to measure it. Adults are usually 54 to 74 mm; we accept 46 to 80.
A labelled example
This is a typical prescription for someone in their 40s who is short-sighted with mild astigmatism. Read across each row: the right eye needs -2.00 with a small cylinder at 180 degrees, and both eyes share a +1.50 reading addition.
- No ADD value? You need single vision.
- An ADD value? Progressives, bifocals or a separate reading pair.
- A CYL always comes with an axis. If one is blank, both should be.
| Eye | SPH | CYL | Axis | ADD |
|---|---|---|---|---|
| Right (OD, R) | -2.00 | -0.75 | 180 | +1.50 |
| Left (OS, L) | -1.75 | -0.50 | 175 | +1.50 |
| PD | 63 (or 31.5 / 31.5 as a dual PD) | |||
SPH main power
CYL astigmatism
Axis its angle
ADD reading boost
Single or dual PD
Both are fine. The configurator accepts either.
Single PD
One number, for example 63. The total distance between your pupils. This is what most opticians write and what the mirror method gives you.
Dual PD
Two numbers, for example 31.5 / 31.5, measured from the centre of your nose to each pupil. More precise if your face is not symmetrical. Choose "I have two PD numbers" in the configurator.
Reading glasses use a near PD, which is about 3 mm less than your distance PD. We work that out for you: always enter your distance PD.
PD in 30 seconds
How to measure your PD
Not on your prescription? Measure it with a ruler and a mirror, or use the PD tool, which does it with your camera.
- 1
Stand about 30 cm from a mirror, looking straight ahead.
- 2
Hold a millimetre ruler against your eyebrows, resting on the bridge of your nose.
- 3
Close your right eye and line the zero up with the centre of your left pupil.
- 4
Open both eyes, close your left eye, and read the millimetres under the centre of your right pupil.
- 5
That number is your PD. Repeat twice to be sure it matches.
- Adult PDs almost always fall between 54 and 74 mm. If yours reads far outside that, measure again.
When a prescription expires
Most UK opticians date a glasses prescription for two years from the sight test; some give one year if your eyes are changing. The expiry is usually printed on it. We can make glasses from a prescription that is in date. If yours has expired, book a sight test first: your eyes have probably changed, and new lenses to old numbers are money wasted.
Contact lens prescriptions are different
A contact lens prescription sits on the eye, so its numbers are not the same as a glasses prescription, and it will not have a PD. Please send the glasses one. If you are not sure which you have, upload it and we will tell you.
Upload tips
A clear photo means we can confirm your numbers back to you the same day.
- Lay the prescription flat in good light, with no shadow across it.
- Get all four corners in the photo, straight on, not at an angle.
- Make sure both the right and left rows are readable, including the signs (+ and -).
- Include the optician's name and the date of the sight test if they are printed on it.
- A screenshot of an emailed prescription or a scan is fine too.
- If your PD is not on it, add it in the PD box or measure it with the PD tool.
Prefer to type it? The configurator has a form with every value as a dropdown, and it flags the classic copying mistakes (a CYL with no axis, one eye plus and one minus) before you pay. You can also send the prescription later by email and we will hold the order.
How try-on works
Your camera, your face, nothing stored
The live try-on runs entirely in your browser. Your camera feed is processed on your device to find your eyes and place the frame at true scale. Nothing is recorded, uploaded or sent anywhere.
If the camera is not an option, upload any photo of yourself and position the frame by hand. The photo never leaves your device either.
