Understanding Your Contact Lens Prescription

Essential Abbreviations in Your Contact Lens Prescription

Your contact lens prescription will typically include several abbreviations. Here's a guide to some of the most common ones you may encounter:

• 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 

Although many of these abbreviations are also used in eyeglass prescriptions, contact prescriptions have some extra details. The number next to SPH or PWR shows the strength of your lens in diopters. A plus (+) sign indicates farsightedness, while a minus (-) sign means nearsightedness.

If you have astigmatism, which occurs when your cornea is irregularly shaped, your prescription will include "CYL," indicating how much cylindrical power is needed to correct it. "Axis" shows the specific angle of the cylindrical lens. If you don’t have astigmatism, you may see "DS," indicating your eyes are normally spherical.

Lastly, "ADD" will be included if you need additional correction for bifocal, multifocal, or progressive lenses.

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

Although contact lens prescriptions use some of the same abbreviations as eyeglass prescriptions, they also include measurements tailored for the fit of contact lenses on your eyes. Here are a couple of extra abbreviations to look out for:

• BC: Base curvature 

• DIA: Diameter 

"BC" refers to the curvature of your cornea. Your contact lens curvature must match your cornea’s for a proper fit and comfort. "DIA" measures the diameter of the contact lens in millimeters, ensuring the lens fits properly on your eye.

Additionally, your contact lens prescription will list the brand of lenses prescribed and the expiration date of the prescription.

If you have both an eyeglass and contact prescription, you may notice that the numbers for the same eye differ. This is because glasses rest slightly away from your eyes, while contact lenses sit directly on your cornea. Therefore, each prescription is adjusted to account for how each lens type interacts with your eyes for optimal vision correction.

How Your Eye Doctor Will Explain Your Prescription

When you receive your contact lens prescription, your eye doctor will take the time to explain why they’ve chosen a specific type of lens for you. For example, if you have astigmatism, your doctor may suggest toric lenses to correct the irregular shape of your cornea. If you need assistance with both near and far vision, multifocal lenses might be the most suitable option. At Nationwide Vision, we offer a variety of specialty contact lenses tailored to different vision needs.

Your prescription will also specify the brand of contact lenses your doctor recommends. This choice is based on factors like the shape of your cornea, the complexity of your prescription, whether you have dry eyes, and other individual considerations.

Additionally, your doctor will discuss why you may have chosen contact lenses over glasses or if you plan to use both. Together, based on your specific needs and prescription, you’ll select the contact lenses that provide the best fit, comfort, and visual clarity.