PWR: the power
PWR (sometimes written SPH) is the strength. Negative numbers (-0.50 to -12.00) correct short-sightedness. Positive numbers correct long-sightedness. Plano, written 0.00, means no correction at all. A plano lens is still a medical device and still needs to fit, but it does not change how well you see.
BC: the base curve
BC describes how curved the back of the lens is, in millimetres. Most people sit between 8.4 and 8.8. A lens that is too flat slides; one that is too steep feels tight and can trap air. This is the number people ignore most often when switching brands, and it is the one that decides comfort.
DIA: the diameter
DIA is the full width of the lens. For coloured lenses, the more useful number is the graphic diameter, which is the printed area. A 14.2 mm lens with a 13.6 mm graphic sits inside a normal iris outline; a 14.5 mm lens with a 13.8 mm graphic enlarges more.
CYL and AXIS: astigmatism
If you have astigmatism, two extra numbers appear. CYL is the amount of correction and AXIS is the angle, from 1 to 180 degrees. Coloured toric lenses exist but the range is narrower than clear lenses, so check availability before you choose a shade.
Matching a coloured lens to your prescription
Write down PWR, BC and DIA from your current lenses, then compare with the product page. The base curve should match exactly. Power should match exactly. Diameter can vary within about 0.3 mm without a new fitting, but if you go larger for the look, expect a different feel for a few days.
Frequently Asked Questions
Can I use my glasses prescription for contacts?
No. A glasses prescription contains values that do not transfer directly, especially for high powers and astigmatism. You need a contact lens prescription.
What if my prescription is not available in a shade I like?
Choose the shade range that covers your power first. Wearing a lens that does not match your prescription is never worth the look.
Does 0.00 power mean I can wear any coloured lens?
It means no vision correction, but base curve and diameter still have to suit your eye.
