If you’ve ever walked out of an eye exam holding a slip of paper covered in numbers, abbreviations, and plus or minus signs and wondered what it all means, you’re not alone. Here’s a plain-language breakdown of the numbers on your prescription and what they tell you about your vision.
The Minus Sign: Nearsightedness (Myopia)
A minus sign (-) in front of a number means you’re nearsighted, or myopic. This means you can see objects up close clearly, but distant objects — like road signs, whiteboards, or the TV across the room — appear blurry.
The number that follows the minus sign is measured in diopters, a unit that describes how strongly a lens needs to bend light to correct your vision. The higher the number, the stronger the correction needed, and the more nearsighted you are. A prescription of -1.00 is considered mild myopia, while -6.00 or higher is considered high myopia.
The Plus Sign: Farsightedness (Hyperopia)
A plus sign (+) means the opposite: you’re farsighted, or hyperopic. People with hyperopia often see distant objects reasonably well but may struggle to focus on close-up tasks like reading, sewing, or using a phone, especially for a prolonged period of time. In some cases, especially with mild hyperopia, and in younger patients, the eyes can compensate for hyperopia, which is one reason routine exams matter even when there are no obvious complaints.
Like myopia, hyperopia is measured in diopters, with the number showing how much correction your eyes need.
What About Astigmatism?
If your prescription has a second number labeled Cyl (short for cylinder), that’s your astigmatism correction. Astigmatism happens when the cornea and/or lens of the eye causes light to focus at more than one point instead of a single spot. This can lead to blurry or distorted vision at any distance, along with symptoms like eye strain or headaches.
Alongside the cyl value, you’ll usually see an axis number between 0 and 180. This tells your optician the exact orientation of the astigmatism so your glasses can be shaped correctly to compensate.
Other Common Abbreviations
- OD (Oculus Dexter): Your right eye
- OS (Oculus Sinister): Your left eye
- OU (Oculus Uterque): Both eyes
- ADD: An additional magnifying power, typically for reading, often seen in prescriptions for patients over 40 who need help with near vision (presbyopia)
- PD (Pupillary Distance): The distance between your pupils, used to properly center your lenses
Why Understanding Your Numbers Matters
Knowing how to read your own prescription helps you track changes in your vision over time, understand why your prescription strength has changed, and feel more confident asking your optometrist questions during your exam. It’s also useful when comparing options for glasses or contact lenses, since not every prescription translates directly between the two.
Every number on that slip of paper is there to help build lenses that are precisely tailored to your eyes. If you ever have questions about what your specific prescription means for your day-to-day vision, our doctors at The EyeSite are always happy to walk through it with you during your next comprehensive eye exam.