How to Read Your Glasses Prescription
A glasses prescription is a few abbreviations and numbers for each eye: sphere, cylinder, axis, add, prism and pupillary distance. Here we explain what every value means, with an example prescription, so you understand your own and can enter it correctly when you order glasses online.
How do you read a glasses prescription?
Read the prescription line by line: OD or R is the right eye and OS or L is the left eye. Sphere (SPH) is the main lens power in diopters, where minus means nearsighted and plus means farsighted. Cylinder (CYL) and axis (AX) correct astigmatism. Add (ADD) is extra power for close-up vision, and pupillary distance (PD) is the distance between your pupils in millimeters. Empty fields mean you do not need that correction. See the example below
What does a glasses prescription look like?
This is how a glasses prescription from an optician can look. The numbers in the table header match the explanations below the table.
| 6Eye | 1Sphere (SPH) | 2Cylinder (CYL) | 3Axis (AX) | 4Add (ADD) | 5Prism / base |
|---|---|---|---|---|---|
| Right (R / OD) | −2.25 | −0.50 | 180 | +1.50 | – |
| Left (L / OS) | −1.75 | −0.75 | 10 | +1.50 | – |
What do the abbreviations on a glasses prescription mean?
Opticians use slightly different abbreviations, in English, Latin or the local language. The table shows the common variants.
| Abbreviation | Meaning | What it looks like |
|---|---|---|
| OD, R, RE | Right eye (OD comes from the Latin oculus dexter) | The row for the right eye |
| OS, L, LE | Left eye (OS comes from the Latin oculus sinister) | The row for the left eye |
| OU | Both eyes (oculus uterque) | The same value for both eyes |
| SPH, Sphere | The main lens power in diopters | −2.25 or +1.50 |
| PL, Plano, 0.00 | No spherical power | 0.00 |
| CYL, Cyl | Power for astigmatism | −0.50 |
| AX, Axis | The angle of the cylinder in degrees | 180 |
| ADD, Add | Extra power for close-up | +1.50 |
| Prism, Base | Prism power and direction | 1.0 Base out |
| PD | Pupillary distance in millimeters | 63 or 31.5 / 31.5 |
| VA, Visus | Visual acuity with the lenses, not needed when ordering | 1.0 or 20/20 |
What do minus and plus mean on a glasses prescription?
The sphere (SPH) is the most important number on the prescription. It tells how strong the lenses need to be, in diopters, in steps of 0.25.
Minus means you are nearsighted: you see well up close but blurry far away. Plus means you are farsighted: the eye has to work harder, and it is often most tiring up close. The further the number is from zero, the stronger the lenses you need.
If it says PL, Plano or 0.00, that eye needs no spherical power.
What do cylinder and axis mean on a glasses prescription?
Cylinder (CYL) and axis (AX) correct astigmatism, which means the cornea or lens is curved slightly unevenly. The eye then bends light differently in different directions, and vision can be blurry or distorted at every distance.
The cylinder is the power of the correction in diopters. The axis is the angle the cylinder should sit at, from 0 to 180 degrees. The two always belong together: if you have a cylinder you also have an axis, and the other way around.
The cylinder can be written with minus or plus depending on the optician. The same correction can look different on two prescriptions, so copy the values exactly as they are written.
What does ADD mean on a glasses prescription?
Add (ADD) is extra plus power for close-up, added to the sphere when you read. It usually appears on prescriptions from around 40 to 45, when the eye becomes less able to focus up close. This is called presbyopia.
ADD is usually the same for both eyes and often between +0.75 and +3.00. It is used in reading glasses, progressive glasses and sometimes in computer glasses.
You can work out the power for reading glasses by adding the sphere and the add together.
Computer glasses
Computer glasses are made for screen distance, which sits between far and near. Tell your optician you want computer glasses, so the right power for screen distance is on your prescription.
What is pupillary distance (PD) on a glasses prescription?
Pupillary distance (PD) is the distance between the centers of your pupils, in millimeters. It is used to place the optical center of each lens directly in front of your pupils. For most adults it is between about 54 and 74 millimeters.
PD can be written as one or two values. One value, for example 63, is the total distance between the pupils. Two values, for example 31.5 / 31.5, are the distance from the center of the bridge of the nose to each pupil and are called monocular PD. Two values are more precise if the face is not fully symmetrical.
If it says two different numbers, for example 63 / 60, the first is for distance and the second is for near.
What do prism and base mean on a glasses prescription?
Prism is used if the eyes do not fully work together, for example with double vision. The prism shifts the image slightly so the eyes can work together more easily.
Prism power is given in prism diopters, and the base shows which direction the prism should face: in, out, up or down. Most prescriptions have no prism at all, and then the fields are empty.
If your prescription has prism, contact us before you order.
Can I use my contact lens prescription to buy glasses?
No. Contact lenses sit directly on the eye while glasses sit a little in front, so the power is not the same, especially at higher powers. A contact lens prescription also includes values for the shape of the lens that are not used in glasses.
Always use a glasses prescription when you order glasses.
How do I enter my glasses prescription when I order?
With us, you add your prescription on the product page, in the same step as your lens choices. You can upload the prescription as a file or enter the values yourself.
Copy every value exactly as it is on the prescription: the right eye, the right sign (plus or minus) and the right decimal. If the prescription has both cylinder and axis, enter both.
Check before you order
Prescription glasses are made to the values you enter and cannot be returned. Double-check that right and left have not been mixed up, that plus and minus are correct, and ask your optician if anything is unclear.
Questions about glasses prescriptions
How long is a glasses prescription valid?
How long a prescription is valid varies between countries, and vision can change over time. Many opticians recommend a new eye exam every two years, or sooner if you notice your vision has changed.
What is a normal glasses prescription?
There is no normal prescription, since it depends on your eyes. For nearsightedness, up to −3.00 is usually considered mild, −3.00 to −6.00 moderate and over −6.00 high.
Why do my eyes have different prescriptions?
It is common for the right and left eye to have different powers, since the eyes can differ in length or curvature. That is why the prescription has a row for each eye.
What does 0.00 or PL mean on a prescription?
0.00, PL or Plano means the eye needs no spherical power. If there is also a cylinder, the eye still needs correction for astigmatism.
What does it mean if cylinder and axis are empty?
Empty fields for cylinder and axis mean you have no astigmatism that needs correcting. Then the sphere is all you need.
What is the difference between minus and plus cylinder?
They are two ways of writing the same correction. Opticians can write the cylinder with minus or plus, and the sphere and axis change too. Always copy the prescription exactly as written.
What do I do if PD is missing from my prescription?
Ask the optician who did your eye exam. PD is usually measured during the exam even if it is not on the prescription.
Can I work out my reading glasses power from my prescription?
Yes, add the sphere and the add together. With SPH −1.00 and ADD +2.00, the reading glasses power is +1.00.