A prescription can look technical at first glance, but a few pointers are enough to make it easy to read. This guide explains the main fields so you can enter your correction online without stress.
Identifying the eyes: OD, OG and sometimes ODG
On your prescription you will often see abbreviations:
- OD (right eye)
- OG (left eye)
- ODG (both eyes)
If a line is common to both eyes, it may appear under ODG. Otherwise, you will find one line for each eye.
The essential values to enter
Sphere (SPH)
The sphere indicates the main power of your correction:
- Negative value (-): short-sightedness (blurred distance vision)
- Positive value (+): long-sightedness (blurred near vision)
Cylinder (CYL)
The cylinder corrects astigmatism. It can be negative or positive, depending on how the prescription was written.
Axis
The axis is an angle expressed in degrees (from 0 to 180). It always accompanies a cylinder and specifies the orientation of the astigmatism.
Addition (ADD)
The addition relates to presbyopia. It is added to the sphere for near vision.
Pupillary distance (PD)
The pupillary distance is the distance between your pupils, measured in millimetres.
- Sometimes written EP or PD
- It may be given as a binocular value (a single figure) or monocular values (two figures, right and left)
If you have two values (for example 32 / 32), you can enter them separately. If you only have one value (for example 64), it can be split into two equal values.
A simple example to find your bearings
You might see a prescription with this kind of information:
- OD: -1.25 (SPH) / -0.50 (CYL) / 90 (AXIS)
- OG: -1.00 (SPH) / -0.25 (CYL) / 80 (AXIS)
- ADD: +1.50
- PD: 64 mm
This data corresponds to the fields requested when configuring online.
If in doubt
If a value looks odd or seems to be missing, contact us before confirming your order. We can help you read your prescription again.
Going further
How to choose your corrective lenses → Varifocal lenses: who they're for, benefits and price → How to choose glasses to suit your face shape → How to care for your glasses →