How to Decipher Your Contact Lens Prescription

Key Abbreviations to Know

Your contact lens prescription will likely include several abbreviations. Here’s a quick guide to the most common ones:

• OD: Right eye 

• OS: Left eye 

• SPH or PWR: Spherical correction or power 

• Numbers with plus or minus signs: Diopters, a number that measures corrective lens strength. 

• CYL: Cylindrical power 

• Axis: The direction a cylindrical lens needs to be tilted. 

• DS: Diopters sphere 

• ADD: Additional correction 

Many of these abbreviations are also used in eyeglass prescriptions, but with contacts, there are extra details to consider. The number next to SPH or PWR is measured in diopters and represents the strength of your corrective lens. A plus sign (+) indicates farsightedness, and a minus sign (-) indicates nearsightedness.

If you have astigmatism, which is caused by an irregularly shaped cornea, your prescription will also include “CYL,” which indicates the strength required to correct this condition. “Axis” refers to the direction in which the cylindrical lens needs to be oriented. If you don’t have astigmatism, your prescription might list “DS,” meaning your eyes have a normal, spherical shape.

Finally, “ADD” refers to additional correction and is usually added for people who need bifocals, multifocal lenses, or progressive lenses.

What Makes a Contact Lens Prescription Different from an Eyeglass Prescription?

While contact lens prescriptions share some abbreviations with eyeglass prescriptions, they also include extra measurements to account for the way contacts fit your eye. Here are a couple of additional abbreviations you may see: 

• BC: Base curvature 

• DIA: Diameter 

"BC" refers to the curvature of your cornea, and it’s crucial that the contact lens matches this curvature for proper fit and comfort. "DIA" describes the diameter of the contact lens, measured in millimeters, ensuring the lens fits correctly on your eye.

Your contact lens prescription will also list the brand of lenses prescribed, as well as an expiration date for the prescription.

If you have both eyeglass and contact prescriptions, you may notice that some of the numbers are different even for the same eye. This is because glasses and contacts are worn differently—glasses rest a bit away from your eyes, while contacts sit directly on your cornea. Because of this difference in distance, prescriptions are adjusted accordingly to provide the best vision correction for each type of lens.

How Your Eye Doctor Will Explain Your Prescription

When you receive your contact lens prescription, your eye doctor will carefully explain why they’ve chosen a particular lens type for you. For example, if you have astigmatism, they may recommend toric lenses to correct the irregular shape of your cornea. If you need a solution for both near and far vision, multifocal lenses might be the right choice. eyecarecenter offers a variety of specialty contact lenses tailored to meet different eye care needs.

Your prescription will also include the specific brand of contact lenses your doctor recommends. This choice could be based on several factors, including the shape of your cornea, the complexity of your prescription, your experience with dry eyes, and other unique considerations.

Additionally, your doctor will discuss why you’ve chosen contacts over glasses or why you may want to use them in addition to glasses. Together, based on your prescription and individual needs, you will select contact lenses that offer the best comfort, fit, and vision correction.