How to Read Your Contact Lens Prescription?

Your contact lens prescription is more than just a piece of paper. It’s a detailed roadmap to clear, comfortable vision. But it can feel overwhelming at first glance with all of the numbers, abbreviations, and technical terms. Don’t worry! We’re here to simplify it for you. 

Let’s explain how to read your contact lens prescription and what each figure means.

Step-by-Step Guide to Reading Your Contact Lens Prescription

Need an Image Here. SENT IMAGE, USE THE CONTACT LENS ON THE HAND 

1. OD and OS: Which Eye Is Which?

• OD stands for oculus dexter, which means your right eye.

• OS stands for oculus sinister, which means your left eye.

• These abbreviations tell you which part of the prescription applies to which eye. If you see “OU,” it means both eyes.

2. Sphere (SPH): Correcting Nearsightedness or Farsightedness

• The sphere value (SPH) indicates the lens power needed to correct your vision.

• A negative number (e.g., -2.50) means you’re nearsighted (you have trouble seeing distant objects clearly).

• A positive number (e.g., +1.75) means you’re farsighted (you have trouble seeing close-up objects clearly).

• For example, a sphere of +0.25 means you are slightly farsighted.

3. Cylinder (CYL) and Axis: Correcting Astigmatism

• If you have astigmatism, your prescription will include a cylinder (CYL) and axis value.

• CYL measures the degree of astigmatism (an irregularly shaped cornea). This  number will be negative.

• An axis is a number between 0 and 180 that indicates the orientation of the astigmatism correction.

• For example, a CYL of -1.50 and an axis of 90 means your cornea is irregularly curved, and the correction is oriented at a 90-degree angle.

4. Add: Multifocal Lenses for Presbyopia

• If you need multifocal lenses, your prescription will include an Add value.

• This number indicates the additional magnifying power required for close-up tasks, like reading or using your phone.

• For example, an Add of +2.00 means you need extra power for near vision.

5. Base Curve (BC): Ensuring a Comfortable Fit

• The base curve (BC) describes the curvature of your contact lens.

• It ensures the lens fits comfortably on your eye.

• Common base curve values range from 8.0 to 9.0.

6. Diameter (DIA): Covering Your Cornea

• The diameter (DIA) measures the width of the lens.

• It ensures the lens fully covers your cornea.

• Typical diameters range from 13.5 to 14.5 millimeters.

Example Prescription: Putting It All Together

Let’s look at an example to see how these values come together:

This prescription shows the patient has astigmatism (CYL and Axis values) and requires multifocal lenses (Add value).

Why Are These Measurements Important?

Each figure on your contact lens prescription ensures your lenses fit properly and provide clear vision. Here’s why they matter:

• Sphere (SPH): Corrects your overall vision, whether nearsighted or farsighted.

• Cylinder (CYL) and Axis: Address astigmatism by compensating for the irregular shape of your cornea.

• Add: Provides additional power for close-up tasks if you have presbyopia.

• Base Curve (BC) and Diameter (DIA): Ensure your lenses sit comfortably and remain appropriately placed on your eyes.

Without these precise measurements, your contact lenses might not fit or center well, leading to discomfort or blurred vision. To maintain the best lens performance, it’s also essential to use a high-quality cleaning and disinfecting solution as appropriate like Tangible Clean, which helps keep your lenses deposit-free and comfortable.  Of course if you select single use daily disposable contact lenses, you won’t need to worry about solutions.

As proper care is also key — certain specialty contact lenses require the use of  Lacripure, a preservative-free saline solution.  Using Lacripure with specialty contact lenses upon insertion ensures your lenses remain clean and comfortable, providing good vision throughout the day.

How To Read a Contact Lens Prescription for Astigmatism

If you have astigmatism, your prescription will include cylinder (CYL) and axis values. These numbers ensure your lenses correct the irregular shape of your cornea. For example:

• CYL: -1.50 (degree of astigmatism)

• Axis: 90 (orientation of the correction)

Without these values, your lenses won’t provide clear vision for astigmatism.

How To Read a Multifocal Contact Lens Prescription for Presbyopia

Multifocal lenses are designed for people with presbyopia, a condition that makes it difficult to focus on close-up objects. Your prescription will include an “Add” value, which indicates the additional magnifying power needed for reading. For example:

• Add: +2.00 (additional power for near vision)

How To Read a Contact Lens Prescription on the Box

The prescription details are usually printed on the box when you receive your contact lenses. Look for labels like:

• PWR: Power (sphere)

• BC: Base curve

• DIA: Diameter

• CYL: Cylinder (if applicable)

• AX: Axis (if applicable)

• ADD (if applicable)

These values should match your contact lens prescription exactly.  They may NOT match your glasses prescription.  Often the two prescriptions are different.

Contact Prescription FAQs

1. Why Do Contact Lenses Require a Prescription?

Contact lenses are medical devices that rest directly on the surface of your eye. A prescription ensures they’re safe, effective, and tailored to your vision needs.

2. How Do I Get a Contact Prescription?

You’ll need a comprehensive eye exam from an optometrist. At Vision Source Rio and Vision Source Heights, our experienced team provides thorough eye exams and personalized contact lens fittings to ensure you get the best prescription and vision.

3. Where Is the Power on My Contact Prescription?

The power is listed under “Sphere (SPH)” on your prescription.

4. Are Glasses and Contact Prescriptions the Same?

No, glasses and contact prescriptions are not the same. Contact lens prescriptions include additional measurements like base curve and diameter.

5. How Do I Know Which Contact Is for Which Eye?

Your prescription will specify “OD” for the right eye and “OS” for the left eye.

6. What if My Contact Prescription Is Expired?

Expired prescriptions are no longer valid. You’ll need to schedule an eye exam to renew your prescription.

Expired prescriptions are no longer valid, so you’ll need to schedule an eye exam to get a new one. Most eyeglass and contact lens prescriptions are typically valid for 12 months, though this can vary depending on your age and eye health.

7. What Does Sphere +0.25 Mean?

A sphere of +0.25 indicates you are slightly farsighted.

8. What Do OS and OD Mean for Contacts?

OS stands for oculus sinister (left eye), and OD stands for oculus dexter (right eye).

Why Choose Vision Source Rio and Vision Source Heights for Your Contact Lens Needs?

75% of adults use some form of vision correction, and contact lenses are popular for convenience and comfort.  With our state-of-the-art technology and expert care, we’ll ensure your contact lenses fit well and provide you with the best possible vision. 

At Vision Source Rio and Vision Source Heights, we’re committed to providing personalized eye care and helping you find the perfect contact lenses for your lifestyle. Whether you need lenses for astigmatism, presbyopia, or everyday wear, our team will guide you every step of the way.

Ready to Get Started?

Don’t let confusion about your contact lens prescription hold you back. Schedule an eye exam with Vision Source Rio or Vision Source Heights today and take the first step toward clearer, more comfortable vision. Visit our Vision Source Rio or Vision Source Heights website to book your appointment today!

Your eyes deserve the best care—let us help you see the world more clearly!