Precision Vision Contacts

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Power on your prescription is a number, that starts with a + or - sign. For example, +3.50, -2.75 etc. This is to correct either your nearsightedness if it is a (-) sign or farsightedness if it is a (+) sign.

Base Curve, (BC) is a measure of the curvature of the contact lens. This makes the lens fit more comfortably on your cornea. Typically BC is in the range 8.3 to 9.0.

Diameter is a measure of the size of the lens. Typically Diameter is in the range of 14.0 to 14.5.

Sometimes, a lens is manufactured in only one base curve or diameter. Your optician may then have omitted this value on your prescription since it makes no difference anyway.

The right eye is abbreviated OD, the left OS and both eyes are OU.



Cylinder (Cyl) Is the strength of your astigmatism. If you have a number for cylinder on your prescription you should look at our Toric Lenses. Typical numbers for cylinder are -0.75, -1.00, -1.25.


Axis Is the orientation of your astigmatism on your cornea. Typical numbers for Axis are 160, 170, 080.

Add power is the second power correction you need if you are wearing bifocal contact lenses. This number refers to the reading strength of the lens. Typically addpower is in the range of +1.00 to +2.50.


Colour is the colour of the contact lens and is only needed if you are buying coloured or special effect contact lenses. The colour does not affect your prescription in any way.