Understanding your Prescription

My Prescription Example

Prescription for right and left eye


The sphere (Sph) specifies the strength of lens required to correct your focus. If there is a (+) in this box then that means that you are long-sighted. If there is a (-) is this box then you are short-sighted. The sphere is measured is dioptre. Your prescription could also have the word plano, PL or an infinity sign - this means that you are neither long- nor short- sighted.

Cyl and Axis

A value in the cylinder (Cyl) and axis means you have astigmatism. Astigmatism occurs when the eye is shaped slightly like a rugby ball (also known as “toric”) rather than a spherical shape like a football. This means that the eye has difficulties in focusing on certain angles. The cylinder is measured in dioptre and the axis is measured in degrees.


A prism is required to correct a lazy eye and to correct some special conditions or eye disorders. It is measured in dioptre.

Inter Add

This refers to intermediate vision that needs correcting. This correction is often used for computer (VDU) use.

Near Add

A value in this is to correct your near vision. This correction is often used for reading or any detailed close work.


Also known as Back Vertex Distance is the distance between the back of the spectacle lens and the front of the cornea (front surface of the eye). This correction is often seen with higher prescriptions. It helps to not see blurred images.


PD or Pupillary Distance is the distance from the centre of one pupil to the centre of the other pupil. It is measured in millimetres (mm) and ranges from 50 to 70mm. Having this information helps to produce prescription glasses with "100% accuracy" as it allows us to measure the point on the lens where it performs the best and has the least distortion. That point will be the clearest part of your lenses when placed in your frame.