How to Decipher Your Prescription’s Numbers

When you look the eyeglasses prescription your ophthalmologist gave you, do you find the numbers confusing? It’s quite plausible, because there’s such a large variety of needed vision corrections. An ophthalmologist has carefully calculated those numbers to provide you with the lenses that are particular to your eyesight. 

At the office of Glaucoma Consultants of St. Louis, we use our extensive knowledge of the ocular system and the complexities of the eye to fit you with the perfect lenses. Our team is made up of friendly, highly trained specialists who are eager to help you feel comfortable and relaxed while benefitting from the very best in care. 

Prescriptions for eyeglasses are categorized under OS and OD, which are Latin abbreviations for the left eye (oculus sinister) and the right eye (oculus dextrus), respectively. It may say OU (oculus uterque), which refers to both eyes.

The higher from zero indicates the prescription strength—a stronger prescription. The plus sign (+) before the number means you’re farsighted, while a minus sign (-) means you’re nearsighted. These numbers are diopters (D), the units that gauge the strength of improvement. 

For instance, if the prescription says -1.00, there’s one diopter of nearsightedness, which is quite minor. If it says -4.25, there are four-and-a-quarter diopters of nearsightedness, and stronger lenses will be needed. Correspondingly, +1 denotes slight farsightedness and +5 means more. 

People with astigmatism have three numbers: S x C x Axis. (Astigmatism most often is caused by a cornea shaped more like a football than a basketball.) The S pertains to the spherical meaning (the degree of nearsightedness or farsightedness). The C (cylinder) measures in diopters astigmatism; its number can be positive or negative. The bigger this number, the more astigmatism. The Axis, between 0 and 180 degrees, tells the orientation of astigmatism.

Now that you know how to decode an ophthalmologist’s prescription, you won’t be left wondering what all those numbers mean. 

The office of Glaucoma Consultants of St. Louis is committed to the eye health of all of our patients. We’ve earned the trust of all of our patients and look forward to earning yours. For more information about our practice, please don’t hesitate to call us today.

By Glaucoma Consultants of St. Louis

January 27, 2022