If you have vision problems, wearing prescription glasses might help. When you receive a prescription, you want to understand what the prescription numbers mean and how to read them. Here's how eye care professionals use the numbers to determine the best type of lens for patients.  

What the Numbers Mean on a Glasses Prescription

A typical prescription lists two acronyms, one for each eye. Oculus dexter, O.D., is your right eye, and oculus sinister, O.S., is your left eye. Generally, eye doctors write glasses prescriptions with two different numbers: sphere (SPH) and cylinder (CYL). SPH measures whether you are nearsighted or farsighted and the lens power needed to correct your vision. 

CYL indicates whether you have astigmatism, and if so, how much. A normal eye is round, and the cornea curve stays the same when the eye rotates. An eye with astigmatism is shaped like an egg or a football, with one curve longer than the other. The CYL number corrects the second curve to match the first. 

Axis numbers are in degrees between 1 and 180. The axis tells you where the astigmatism is on the cornea and which way the astigmatism lines up. If you experience double vision, meaning you see two images of an object, you need prism correction. The prism combines the two images, so you see only one. 

How to Read the Prescription

Lens power is measured in diopters. If you consider the measuring system is like a number line, zero in the middle means no corrections are needed. When the sphere field is written as −9.00 D, it means 9 diopters of nearsightedness. A minus sign (−) next to the number indicates nearsightedness, meaning you see better up close and need distance correction. 

A plus sign (₊) shows farsightedness, which means you see better far away and your near vision needs correcting. A number further away from the zero, on either the minus or plus side, means the glasses prescription is stronger.

If you have vision problems, get help from Klecker & Robbins in Lexington, KY. With more than 60 years of experience as optometrists, this father-daughter team is skilled in providing the latest diagnoses and prescription glasses. They offer each patient a personal approach and custom solutions. Visit their website for more information on services, including exams and glasses. Call (859) 269-6921 to schedule an appointment.