How to read your contact lens prescriptions

Your contact lens prescription allows you to purchase your favourite contact lenses that match your contact lens specifications from optometrist or online suppliers.

You should be given written prescription after a routine contact lens fitting, if you were not given a prescription, it is your legal right to have a copy, so do not be afraid to ask your optometrist or optical store staff for it.

How do I read my prescription?

Your contact lens prescription can be found via:

1. the written prescription your optometrist gives you during a check-up
2. on the end/side of your contact lens box
3. on the blister packs that contain your contact lenses.

A written prescription usually includes the following specifications: base curve, diameter, power (or sphere), and then additional figures for Cylinder and Axis if you have an astigmatism, and Addition (Add) and Dominant design ( called Distance D or Near bias N ) for presbyopia correction.

The prescription for your right and left eye will be listed separately as they can vary.

Example prescription:

Name & expiry date: Your prescription should also contain the name of your contact lens e.g. Dailies Total 1 and an expiry date, which is usually a year from the date of your check-up.

Below is an example of the prescription listed on the side of the box or blister pack for DAILIES AquaComfort Plus Toric.

What does each prescription figure mean?

Base Curve (BC): The base curve determines what type of fit is required for the lens to meet the curve of your eye; this is usually written in millimeters or sometimes with the words: flat, median or steep.

Diameter (DIA): The diameter of the contact lens is also written in millimeters and determines the width that best fits your eye.

Power/Sphere (PWR/SPH): This figure shows whether you are long or short-sighted and how much correction your eyes require. If you are long-sighted your figure will begin with a + (plus sign) and if you are short-sighted it will begin with a – (minus sign). This will be followed by a number that goes up from 0 in measures of 0.25 dioptres, the higher the number the stronger the visual correction needed (this value can be displayed on the box as “PWR” or “D”).

Prescription Figures for Astigmatism

The below figures are only displayed on contact lens prescriptions where there is a need for astigmatism correction.

Cylinder (CYL): The cylinder will always been a minus number that increases in measures of 0.25. Much like the power/sphere figure that is shown on all standard prescriptions, the cylinder denotes the extra visual requirements needed for astigmatism and how severe the astigmatism is.

Axis (AX): Astigmatism is caused by the irregular curvature of the eye; the axis is a figure which determines the angle of the correction needed in order to see clearly. The Axis is always a number between 0 and 180 degrees.

Prescription Figures for Presbyopia

The below figures are only displayed on contact lens prescriptions where there is a need for presbyopia/multifocal correction.

Addition (ADD): If you need reading glasses for your near vision also known as presbyopia, the Addition figure determines what level of correction you need to be able to see clearly at a close distance. This is a number between 0.50 and 3.00, some contact lens brands refer to this as a high, medium or low.

Dominant: If you wear multifocals or bifocals your lens correction is determined by a dominant and non-dominant eye, this is the dominant figure usually marked with a “D” and “N” to express which eye is which.