Key Takeaways
- OD refers to your right eye, and OS refers to your left eye on any glasses prescription.
- Numbers closer to zero mean a milder prescription; higher numbers mean stronger correction.
- ADD is extra power for close-up or reading vision, which is more common after age 40.
- Glasses and contact lens prescriptions are different and cannot be used interchangeably.
You leave your eye exam with a small slip of paper covered in abbreviations and numbers, and at first, it makes no sense at all. It’s completely normal not to understand what your glasses prescription means, but our team at Insight Eyecare is here to help make sense of those numbers, so you feel confident and informed.
A glasses prescription is a set of measurements that tells a lens maker exactly how to correct your vision, with specific numbers for each eye based on what the eye doctor found during your comprehensive eye exam. Once you know what each part means, it becomes a lot easier to read.
What the Letters on Your Prescription Mean
The first thing you’ll notice on your prescription is two abbreviations down the left side. OD stands for the Latin term for the right eye, and OS stands for the left eye. Each row of numbers beside those abbreviations applies only to that specific eye.
Your two eyes don’t always need the same correction. One eye might be more nearsighted than the other, or only one eye might have astigmatism. That’s why your prescription has a separate row for each eye rather than a single set of numbers for both.
What the ADD Number Means
Not every prescription has an ADD number. When it does appear, it means your lenses need extra power in a specific zone to help you see things up close, like reading a menu or a phone screen.
You’ll find ADD on prescriptions for bifocal or progressive lenses. It’s common for people over 40, since the eye’s natural focusing ability tends to shift with age. ADD is typically listed as a positive value and indicates the additional lens power needed for near vision.
Is Your Prescription Strong or Mild?
How to Read Your Numbers
The closer your SPH number is to zero, the milder your prescription. A number like +0.50 or -0.75 means your eyes need only a small amount of correction.
The farther the SPH number is from zero, the greater the amount of spherical correction. For example, -6.00 represents more correction than -1.00.
What a Low Number Like +0.25 or -0.75 Means
A small prescription generally means you need a relatively small amount of refractive correction. Some people with low prescriptions notice little difference without glasses, while others may notice blur or visual discomfort during specific tasks.
If you’ve recently picked up new glasses and things still look a bit off, the typical adjustment timeline for new glasses can help you know what to expect.
Glasses vs. Contact Lens Prescriptions
If you’re thinking about switching between glasses and contacts, it’s worth knowing that the two prescriptions are not the same thing. A contact lens prescription includes additional measurements for fit and size, since the lens sits directly on your eye rather than in a frame in front of it. Using one in place of the other won’t give you the correct correction.
Book Your Eye Exam
Our optometrists in South Surrey and White Rock can walk you through your prescription and help you understand exactly what each number means for your eyes. If anything on your prescription still feels confusing, our team at Insight Eyecare is happy to explain it in plain language and help you find the right option for how you live and see. Ready to update your prescription? Book your eye exam today.
