How to obtain a precise eyeglass prescription?
How to Read Eye Glass PrescriptionYou don’t need a medical degree or training to read eyeglass prescriptions. After completing the eye exam, your doctor will write an eyeglass prescription, which usually includes several abbreviations and numbers. For instance, you will see O.D (right eye), O.S (left eye), O.U (both eyes), CYL for the identification of astigmatism, AXIS, DV, NV, and ADD.
For each eye, there are specific numbers after O.D, O.S, and/or O.U. These are known as spherical correction or SPH – and they are usually measured in diopters. Doctors or eye lab personnel use this number to identify the durability of the lenses to correct your vision.
In addition, you are nearsighted if the number has a (-) minus sign next to it. Similarly, you are farsighted if you see there is a (+) sign. Likewise, regardless of the minus or plus sign, if the number is higher, it means you need a stronger prescription.
What does OD vs. OS mean?When you get eyeglasses prescription, you will see some numbers that are listed under headings such as “OS” and “OD.” OS stands for oculus sinister, which means left eye. Similarly, OD stands for oculus dextrous, which means the right eye.
SPH: It stands for spherical power – describing the degree of farsightedness or shortsightedness. When you have a positive SPH or SPH+, it means you are farsighted. Similarly, if you see a negative or minus SPH on the prescription, it means you are nearsighted.
CYL: it stands for “cylinder” – indicating the power of lens for the correction of your astigmatism. If you don’t see any numerical value in the prescription, it means that your doctor has not found astigmatism.
Axis: If your doctor has considered CYL, there is a need for indicating position, which is done through axis value. Actually, it is a number from 1 to 180 measured in degrees. It is used to determine astigmatism on cornea.
Add: It is used in multifocal lenses. The purpose is the indication of extra magnifying power for the lens’ bottom part.
Prism: It is used by doctors when there is a necessity for eye alignment compensation.