Not sure how to read your eyeglass prescription? The short codes and numbers can look confusing, but each one has a simple meaning. This guide explains SPH, CYL, AXIS, ADD and PD in plain language.
Please note: this guide is for general understanding. Your eye doctor is the right person to explain your own prescription and to test your eyes.
Prescription terms at a glance
| Term | Stands for | What it means |
|---|---|---|
| OD | Oculus dexter | Right eye |
| OS | Oculus sinister | Left eye |
| SPH | Sphere | Main lens power |
| CYL | Cylinder | Extra power for astigmatism |
| AXIS | Axis | Direction of the CYL correction, 1 to 180 |
| ADD | Addition | Extra power for near work and reading |
| PD | Pupillary distance | Distance between your pupils, in mm |
OD and OS: right and left eye
OD is your right eye and OS is your left. Each eye can have a different number, which is normal.
SPH (sphere)
SPH shows the main power of your lens. A minus (−) number is commonly used for short-sightedness, where far objects look blurry. A plus (+) number is commonly used for long-sightedness, where near objects are harder to see. The bigger the number, the stronger the lens.
CYL and AXIS
CYL and AXIS appear together when you have astigmatism, which means the front of the eye is not perfectly round. CYL is the extra power needed, and AXIS is a number from 1 to 180 that shows the direction of that correction. If these boxes are empty, you may not need them.
ADD
ADD is extra power added for close-up work. It is used in reading glasses, bifocals and progressive lenses.
PD (pupillary distance)
PD is the distance between the centres of your pupils in millimetres. It helps the optician place the lenses in the right position in your frame.
Tips before you order glasses
- Get your eyes tested regularly, and whenever your vision changes.
- Keep a clear photo or copy of your latest prescription.
- Check that both eyes and all values are written clearly.
- If anything is unclear, ask your eye doctor or optician.
Choose your frame
Once you have your prescription, pick a frame you will love. Not sure about your style? Read our guide to choosing frames for your face shape.
Frequently asked questions
What does a minus sign mean in a prescription?
A minus power is commonly used to correct short-sightedness, where distant objects look blurry.
What is astigmatism?
Astigmatism is when the front of the eye is not perfectly round, which can blur vision at all distances. CYL and AXIS are used to correct it.
What is PD in an eyeglass prescription?
PD is the distance between your pupils in millimetres. It helps place the lenses correctly in the frame.
How often should I get my eyes tested?
Ask your eye doctor. Many people test their eyes regularly and whenever they notice a change in vision.
Have a question about your glasses?
Call Sagar Optical, Aurangabad, and we will be happy to help.
