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How to Decipher Your Contact Lens Prescription
If you're familiar with glasses prescriptions, you may notice that a contact lens prescription looks a little different. If you're new to contacts and are just beginning to explore vision correction options, the information on your prescription slip might seem overwhelming at first.
The key to understanding your contact lens prescription is learning the abbreviations and numbers included in it. Once you become familiar with the terminology and symbols used, you’ll easily be able to interpret any contact lens prescription you receive.
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.
Frequently Asked Questions About Contact Lens Prescriptions
Why is a specific brand or material listed? Can I switch to something cheaper?
Contact lens prescriptions are brand-specific because fit, water content, and oxygen permeability vary by material. You will work alongside your eye doctor to find a contact lens brand that is both affordable and comfortable.
Can I order contact lenses with my glasses prescription?
No. A glasses prescription lacks essential fit parameters like BC, DIA, and brand material and may list a different power. To order contact lenses, you must have a valid contact lens prescription, which is issued after you complete a fitting with an eye care professional.
How do I know when my contact lens prescription expires?
In the United States, the law requires contact lens prescriptions to be replaced every year. The expiration date of your prescription is usually printed near the bottom or on the back of the prescription form. After that date, you’ll need a new exam and fitting.
What do wear-schedule codes mean?
You may see wear-schedule codes on your prescription, which include 3 possible abbreviations:
Daily Wear (DW): Lenses that are removed each night and reused the next day.
Extended Wear (EW): Lenses approved for overnight use for 1-3 weeks (varies by brand).
Daily Disposable (DD): Single-use lenses that are discarded after each day.
Why are there “D” and “N” columns next to the ADD value on my multifocal prescription?
In some multifocal designs, the lens must be labeled for the Dominant (D) and Non-Dominant (N) eye to balance near and distance vision correctly. During your contact lens fitting, your eye doctor will determine which eye is dominant through testing.
Schedule a Contact Lens Fitting at eyecarecenter
Finding the right contact lenses and achieving optimal vision doesn’t have to break the bank. At eyecarecenter, we provide affordable, high-quality eye care to all of our patients. With a wide range of insurance options and a supportive team, we’ll help you find the ideal contact lenses tailored to your specific needs.
If you’re considering wearing contact lenses, schedule an appointment at your nearest eyecarecenter location today. Our team is here to assist with any questions about contact lens exams, fittings, pricing, and insurance coverage.