Have you ever looked at your eye doctor’s prescription right after getting an eye exam? It’s full of abbreviations and numbers that can be very confusing on first glance. What do the numbers on an eyeglass prescription mean? Today, we’d like to help you understand exactly what you’re reading. Below is a sample of an eyeglass prescription. Following the image is an explanation of these terms and numbers: O.D.: This is the abbreviation for Oculus Dexter, the Latin term that means “right eye.” O.S.: This is the abbreviation for Oculus Sinister, the Latin term that means “left eye.” Sphere/Power: Sometimes abbreviated as SPH/PWR, this is your main eyeglass prescription strength. These are measured in diopters and written in increments of 0.25. The numbers may be positive or negative, based on whether you are farsighted or nearsighted. Cylinder and Axis: Sometimes abbreviated as CYL and AX, these measure the level of astigmatism. Since not everyone has astigmatism, these portions of the prescription are sometimes left blank. The Cylinder number is written on 0.25 increments, and the axis is measured in degrees and written in increments of 1. Also, if you don’t have a Cylinder number, you won’t have an Axis number. ADD: If you need bifocals or reading glasses, there will be a value under ADD on your prescription. This signifies that you aren’t just farsighted or nearsighted. These are also written in increments of 0.25. PRISM: In some cases, a patient’s eyes may be misaligned, causing a condition like double vision. If you have numbers in these columns on your prescription, it means you need prism lenses to help properly align your eyes. A Prism may be horizontal, vertical, or a combination of both, CEENTA Eye Ancillary Services Manager Jay Russell said. If you don’t completely understand all this, don’t worry. The opticians at all 12 of CEENTA’s optical shops are trained to read prescriptions and get you glasses that best suit your needs. When you buy glasses at CEENTA, you should know your vision is in good hands. To find an optical shop near you, visit our Locations page.