ACUVUE^® Blog

How to read contact lens prescriptions

By Dr. Giovanna Olivares, OD, FAAO; Johnson & Johnson Vision Care Director & Staff Writer

You’ll be an expert in just a few minutes

When your eye care professional first hands you your contact lens prescription, it will probably look like a foreign language. But fear not. By the time you’re done reading this blog, you’ll be able to look at a contact lens prescription and explain what all those abbreviations and numbers mean. Why is that important? Well, for one, it helps you understand your eyes, and how they work. But secondly, when your box of contact lenses shows up, it helps you double check that the lenses you received are the ones you ordered. Let’s get started!

What do all the numbers and abbreviations mean?

On the contact lens prescription above, you’ll notice some shorthand that eye care professionals use to quickly communicate which lenses will correct your vision. In the next few sections, we’ll go over them one by one.

Starting with the left column

O.D. is short for oculus dexter, which is Latin for “right eye.” O.S. is short for oculus sinister, which is Latin for “left eye” (though we see nothing sinister about a left eye vs. a right eye).

Now looking at the rows from left to right:

POWER, sometimes labeled as sphere, SPH, or D is the power needed to correct your vision. A minus sign means you’re nearsighted and a plus sign indicates you’re farsighted. The number next to the minus or plus is measured in diopters, a funny word for the way they measure how much correction is needed. It’s also where the abbreviation “D” comes from. If you’re at a zero, it means your vision is just about perfect, you need no correction. The further away from zero you get, the stronger the lens you’ll need to correct your vision.

Illustration of a scale that shows a diopter range for nearsightedness and farsightedness

ADD, or additional lens power needed for reading, is included for people who have presbyopia. You may have noticed that many older people need to hold their phone or restaurant menu at arm’s length to read. This natural loss of the ability to focus or see things clearly up close is a normal part of aging and is corrected by the ADD.

BC, or base curve, is the curvature of your contact lenses. Measured in millimeters, it’s one of the factors that determines how well a lens fits your eye.

DIA, or diameter, is the width of your lenses, also measured in millimeters.

Prescriptions for astigmatism

Since astigmatism occurs when your eye is not uniformly spherical, correcting astigmatism means a few more measurements.

CYL, or cylinder, works similarly to the POWER, or sphere measurement, but indicates that you’ll need a different kind of lens to correct your vision—one that corrects for the unique shape of your eye or eyes. Specifically, cylinder compensates for the degree of astigmatism you have. The higher the number, the more irregular the shape of your cornea.

AXIS is a measurement of the orientation of your personal astigmatism (it’s unique to you). It’s always between 0 and 180 degrees. If you think of astigmatism as your cornea shaped more like a lemon than a baseball, AXIS measures the tilt of the lemon shape.

Names and dates are important, too

A contact lens prescription will have some information that isn’t just about your contact lens fit. For starters, your name. And with that fact, it’s a good time to drive home the point that a contact lens prescription is tailored to your eyes and your eyes only. Your contact lenses should never be shared with anyone else.

The two dates include the date your prescription was issued, and the expiration date of the prescription, which is typically a year later (and different than the expiration date of the contact lenses you’ll purchase).

Can you convert your glasses prescription to a contact lens prescription?

You may be able to find conversion calculators online, but contact lenses are considered medical devices, so you’ll need an eye care professional to write you a prescription specific to contact lenses. Since eye glasses sit away from your eyes and not on them like contact lenses, the prescription can actually be a little bit different. Additionally, glasses prescriptions will not provide the base curve (BC) that's needed for the lens to fit on your eye correctly.

How to get a contact lens prescription

You’ll need to schedule a contact lens fitting appointment. After your appointment, you’ll probably go home with some free trial lenses to try. You’ll typically go back to see the eye care professional after a few days to have the vision, comfort and fit on your eye verified. Then you’ll be given your contact lens prescription.

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Put it all into practice

Congratulations, you now have the knowledge you need to be an expert on reading contact lens prescriptions. Test your newfound knowledge with this example contact lens package. Then, when your next package of contact lenses arrives, you’ll be able to confidently double check the box to make sure your prescription matches the one you got.

About the author

Giovanna E. Olivares, OD, FAAO is the Global Director, Specialty Platforms Research & Development, at Johnson & Johnson Vision Care (JJVC). In this role, she is responsible for overseeing the strategy, design, and development of new products to support the company’s global Astigmatism and Presbyopia platforms. In 2017 under her leadership, Johnson & Johnson Vision Care, launched ACUVUE^{^®} Oasys 1-Day with Hydroluxe^{^®} for Astigmatism and ACUVUE^{^®} Vita^{^®} for Astigmatism to meet our patients’ needs. In 2021, her team launched ACUVUE^® OASYS MULTIFOCAL with PUPIL OPTIMIZED^{^®} design. Recently in September, 2022, she launched ACUVUE^{^®} OASYS MAX MULTIFOCAL for presbyopia patients.

Dr. Olivares joined Johnson & Johnson Vision Care, Inc. in 2004 as Sr. Manager of the R&D Design Clinical Research Group. In this role, she led a multidisciplinary group including Optometrists, Ophthalmologists, Vision Scientists, and Biostatisticians responsible for the development of new innovative contact lens products and clinical methodology. Under her leadership, the group launched several brands including ACUVUE^{^®} ADVANCE for ASTIGMATISM, ACUVUE^{^®} OASYS for ASTIGMATISM, and 1-DAY ACUVUE^{^®} MOIST for ASTIGMATISM. Under her leadership, the first validated patient questionnaire for JJVC was developed, CLUE (Contact Lens User Experience).

In 2010, she was appointed to the position of Director of Professional Education, responsible for developing innovative educational programs across the spectrum of students, eye care professionals, Professional Affairs Consultants, and the company’s Sales & Marketing organizations.

Prior to joining Johnson & Johnson Vision, Dr. Olivares served as the Director of Clinical and Professional Development for Unilens Corp. USA, where she developed contact lens designs for presbyopia. Additionally, she has practiced in an ophthalmology practice, private optometric practice, retail optometry, and as a technical medical consultant at TLC, a center for LASIK surgery.

Dr. Olivares received her BS degree from the University of Rochester and her OD degree from the State University of New York (SUNY). She subsequently completed a post-doctoral fellowship in Ocular Disease management at the SUNY College of Optometry. After her fellowship, she joined the SUNY faculty as an Assistant Professor with clinical and didactic teaching responsibilities in the areas of contact lenses, ocular disease, pediatric/binocular vision, and primary care.

Dr. Olivares is a Fellow of the American Academy of Optometry, has authored numerous scientific articles and has lectured internationally on contact lens technology and fitting for success.

Frequently Asked Questions

FAQs About Read Contact Lens Prescriptions

What does the prescription strength mean?

The higher from zero indicates the prescription strength—a stronger prescription. The plus sign (+) before the number means you're farsighted, while a minus sign (-) means you're nearsighted. These numbers are diopters (D), the units that gauge the strength of improvement.

Is contact prescription weaker than glasses?

Since eyeglasses are usually about 12 millimeters from the eye, the prescriptive power of a contact lens — which is positioned directly on the tear film of the eye — will be slightly less nearsighted. This becomes significantly different with prescriptions of 4D or greater.

Are daily and Bi-weekly contacts the same prescription?

yes—but with a caveat. While the basic prescription (the numbers on your box) will likely be the same, the fit and feel might be different because the lenses are made from different materials.

Can I wear contacts that are lower than my prescription?

Wearing a prescription that is too weak or too strong can cause: Blurry vision.

Can I use my eyeglass prescription to buy contact lenses?

No, contact lenses require additional measurements like BC and DIA, which are not included in an eyeglass prescription. You need a separate contact lens fitting.

Footnotes

* Please note professional eye examination and fitting fees may apply. GCC residents 18 or over only. One trial per person. Eligibility subject to Eye Care Professional approval. Participating Eye Care Professionals only. See link for full terms and conditions.

Important information for contact lens wearers: ACUVUE^® Contact Lenses can be used for vision correction. An Eye Care Professional will determine whether contact lenses are right for you. Although rare, serious eye problems can develop while wearing contact lenses. To help avoid these problems, follow the wear and replacement schedule and instructions on proper lens care. Do not wear contact lenses if you have an eye infection, any eye disease or systemic disease, that may affect the eye, or if you are allergic to any ingredients. If you experience eye discomfort, excessive tearing, vision changes, redness or other eye problems, remove the lens and contact your Eye Care Professional immediately. For more information, including warnings and precautions, carefully read the Instructions for Use.

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