Your eyeglass prescription is full of abbreviations that are not obvious at first glance. Once you know what each column means, it becomes much easier to understand your vision and to compare notes with your optician.
Key takeaways
- OD means right eye and OS means left eye.
- SPH is lens power: a minus sign means nearsighted and a plus sign means farsighted.
- CYL and AXIS describe astigmatism; ADD is extra power for near vision.
- The FTC says you are entitled to a copy of your glasses prescription after your exam, and you can fill it wherever you choose.
A sample prescription
| SPH | CYL | AXIS | ADD | |
|---|---|---|---|---|
| OD (right) | -2.25 | -0.75 | 90 | +1.50 |
| OS (left) | -2.00 | -0.50 | 85 | +1.50 |
This is only an example. The numbers are measured in diopters, a unit of lens power.
What each part means
OD and OS
The American Academy of Ophthalmology explains that O.D. stands for oculus dexter, the right eye, and O.S. for oculus sinister, the left eye.
SPH (sphere)
Sphere is the main lens power. A minus sign (-) means nearsightedness, so you see better up close. A plus sign (+) means farsightedness. The bigger the number, the stronger the correction.
CYL (cylinder) and AXIS
Cylinder measures astigmatism, which happens when the cornea has an uneven shape, like an egg rather than a ball. The axis number, from 1 to 180 degrees, tells where on the eye the astigmatism lies. If those boxes are blank, you may have no astigmatism.
ADD
ADD is extra power for near vision, used for bifocals, progressives and reading lenses. It is common after age 40. Learn more in our guides to eye care after 40 and progressive lenses.
PD (pupillary distance)
PD is the distance between your pupils, used to line up the lenses in your frames. The Cleveland Clinic also covers PD in its guide to reading your prescription.
Your rights to your prescription
The FTC says you are entitled to get a copy of your glasses prescription immediately after your eye exam, whether you ask or not, and that you do not have to buy from the prescriber. Eyeglass prescriptions typically last one to two years depending on state law.
Tips
- Keep a photo of your prescription.
- Bring your prescription and your current glasses when you shop.
- Ask questions if a number looks different from last time.
- Remember that a contact lens prescription is separate; see why a contact lens exam is separate.
Frequently asked questions
Can I use my glasses prescription to buy contacts?
No. Contact lenses need their own prescription, which includes lens details such as base curve and diameter.
Can I take my prescription somewhere else?
Yes. The FTC says you do not have to buy glasses from the prescriber who performed your exam.
Visit Reel Optics in Old Bridge
If you would like help, our team in Old Bridge is here. You can book an eye exam or ask about eyeglasses at Reel Optics Vision Center, 2553 County Rd 516, Old Bridge, NJ 08857. Appointments are recommended for eye exams, and walk-ins are welcome when you are shopping for glasses. See hours and directions on our Old Bridge page, or send us a message.
Related reading
Sources and further reading
- American Academy of Ophthalmology: How to read an eyeglasses prescription
- Cleveland Clinic: Got a new eye prescription? Here’s what it means
- Federal Trade Commission: Buying prescription glasses or contact lenses, your rights
- American Academy of Ophthalmology: Eyeglasses, how to choose glasses for vision correction
This article is general information, not medical advice and not a diagnosis. For questions about your own eyes, talk with your eye doctor.
