how to read the eyeglass prescription to find the 20/20 info

You can find the 20/20 information on an eyeglass prescription only indirectly: the prescription tells you lens correction, while 20/20 is a measure of visual acuity on an eye chart. In short, 20/20 is not usually printed on the prescription itself ; it’s a vision-test result.

How to read the prescription

• OD = right eye, OS = left eye, OU = both eyes.

• SPH tells the main lens power needed; a minus sign means nearsighted, a plus sign means farsighted.

• CYL and Axis relate to astigmatism correction, and Add is for reading help in bifocals/progressives.

Where 20/20 fits

• 20/20 vision means you can read at 20 feet what a person with standard vision can read at 20 feet.

• If someone reads the top-line “E” only, that’s much poorer acuity, like 20/200.

• So the prescription numbers do not convert directly into a 20/20 score; an eye doctor uses a chart to measure that separately.

Practical example

If your prescription says OD -2.00 SPH and OS -1.50 SPH , that means your distance vision needs correction, but it does not tell you whether your uncorrected vision is 20/20, 20/40, or another value. Only the vision exam results can tell you that.

Bottom line

Look for the visual acuity result on your exam paperwork, not on the glasses prescription, if you want the 20/20 number.