Contact lens prescriptions contain various abbreviations and numbers that can be difficult to decipher if you aren't familiar with their meanings. Your prescription will tell you exactly what is wrong with each eye and what your contact lens will be doing to correct it. Each eye likely requires a different lens, so your prescription will outline the requirements of the eyes individually. The amount of information on your prescription will vary based on the type of lens you need.
Step 1
Distinguish between the OD and OS lines. OD stands for oculus dexter, or right eye. OS stands for oculus sinister, or left eye. The numbers in the same row or column as OD or OS refer to the needs of that particular eye. Your prescription may also say OU for oculus uterque---meaning each eye---if your prescription is the same for both eyes.
Step 2
Look for the number labeled "power" or "sphere." The number will have a positive sign or a negative sign in front of it. A positive number indicates hyperopia, or far-sightedness. A negative number indicates myopia, or nearsightedness. The further these numbers are from zero, the greater the correction needed in that eye.
Step 3
Look for the "cylinder" or "cyl" number. This will appear only if you suffer from astigmatism. Like the power line, the number after cylinder may be either positive or negative to refer to hyperopia or myopia. The further the number is from zero, the greater the correction needed.
Step 4
Read the "axis" number, which is present only in prescriptions for astigmatism. It refers to the orientation of the cylinder in the contact lens and is expressed as a degree measurement.
Step 5
Look for an "add" number. This number, which is present only in bifocal contact lens prescriptions, provides a modifier to the "power" or "sphere" value. The value is always a positive number, though it may not be printed with a positive sign in front of it.
Step 6
Find the "BC" or base curve and "dia" or diameter lines. These refer to the size and shape of the contact lens and are measurements that make sure the lens will fit on your eye. The measurements will likely be the same for each eye unless your eyes are structurally different from each other.
Tips and Warnings
- If you have questions about your prescription, ask your optometrist or ophthalmologist.
