How to Read an Eyeglass Prescription

When you've just completed an eye exam and find your eyes’ needs have changed, you need to order a new prescription as soon as possible. That's where your new prescription from your optometrist or ophthalmologist comes in.

The following are some tips on understanding your eyewear prescriptions. 


What do the numbers on my prescription mean?


Your prescription may include a SPH, CYL, Axis, ADD and Pupillary Distance (PD). If your prescription does not include one of those it simply means that you do not require that corrective power. There is a separate prescription for your right eye, and for your left eye.


Right eye parameters


Left eye parameters


Sphere indicates the amount of lens power prescribed for nearsightedness or farsightedness.

Cylinder(CYL) & AXIS

A Cylinder (CYL) and Axis is required to correct Astigmatism. Both parameters will be required together.


This provides magnifying power for reading, progressive and bifocal lenses. You will have the same number for both eyes.


A prism number indicates the amount of prismatic power, measured in diopters, needed to compensate for any alignment problems in your eyes.

Pupillary Distance(PD)

PD is the distance between the centre of one pupil (the central black dot of your eye) to the centre of the other pupil, measured in millimeters.

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