If your optometrist mentioned astigmatism, you likely need toric contact lenses, lenses specially shaped to correct the uneven curvature of the cornea that astigmatism causes. Reading a toric prescription is a little more involved than a standard one because it includes extra values, and those values must be exactly right for the lens to sit correctly and give clear vision. This guide explains what each part of the prescription means so you can understand your own numbers with confidence.
The values on a contact lens prescription
A contact lens prescription is different from a spectacle prescription, so always use the one written specifically for contacts. The key values are:
- SPH (Sphere): the main power that corrects short- or long-sightedness, in dioptres. A minus sign means short-sighted, a plus sign long-sighted.
- CYL (Cylinder): the amount of astigmatism correction. This value is what makes a lens toric, a standard lens doesn’t have it.
- AXIS: a number from 0 to 180 that tells the lens which direction the astigmatism runs. It only appears when there’s a CYL value.
- BC (Base Curve): how curved the lens is, to match the shape of your eye.
- DIA (Diameter): the overall width of the lens.
Why CYL and AXIS matter so much for toric lenses
In a toric lens, the correction is oriented in a specific direction, so the lens has to stay rotationally stable on your eye. That’s why both the CYL (how much astigmatism) and the AXIS (which direction) must match your prescription precisely. Order a toric lens with the wrong axis and your vision will be blurry even though the lens “fits.” This is also why toric lenses are designed with weighting that keeps them correctly aligned as you blink.
A worked example
Suppose your prescription reads: SPH −2.00, CYL −0.75, AXIS 180, BC 8.6, DIA 14.5. That describes a short-sighted eye (−2.00) with a moderate amount of astigmatism (−0.75) oriented horizontally (axis 180), on a lens curved at 8.6 and 14.5 wide. Every one of those six numbers needs to be carried across correctly when ordering. When you find lenses, enter all the toric values exactly as written rather than rounding or guessing, because small differences change the correction.
When to see your optometrist
Reading the prescription is something you can do yourself, but the prescription itself must come from a proper eye examination and contact-lens fitting. Astigmatism correction in particular needs professional measurement, and prescriptions expire, an out-of-date one may no longer match your eyes. If you don’t have a current contact-lens prescription, or your vision through your lenses isn’t sharp, book an eye test before ordering.
Frequently asked questions
Can I use my glasses prescription to order toric contacts?
No. Contact lens prescriptions include base curve and diameter and may differ in power because the lens sits on the eye rather than in front of it. Always use a prescription written for contact lenses.
What if my prescription has no CYL or AXIS?
Then you likely don’t have significant astigmatism and don’t need toric lenses, a standard spherical lens will do. CYL and AXIS only appear when astigmatism is being corrected.
Does the axis number need to be exact?
Yes, the axis tells the lens which direction to correct. Toric lenses come in set axis steps, so order the value on your prescription (or the nearest available step your optometrist confirms is suitable).
A toric prescription is just a standard one plus two extra numbers, cylinder and axis, that pinpoint your astigmatism. Understand all six values, copy them exactly when ordering, and keep your prescription current, and your toric lenses will give you crisp, comfortable vision.