Receiving a prescription from your eye doctor can be an exciting moment, especially if you’re about to get new glasses or contact lenses! However, deciphering all those numbers and abbreviations can seem like reading a foreign language. Don’t worry — it’s not as complicated as it appears. In this CristalesGafas article, we’ll guide you step by step through each component of your prescription so you know exactly what those terms mean for your vision.
Key Terms and Common Abbreviations
Before diving into the numbers, it’s essential to familiarise yourself with the abbreviations you’ll commonly find:
- OD (Oculus Dexter): Refers to your Right Eye.
- OS (Oculus Sinister): Refers to your Left Eye.
- OU (Oculus Uterque): Indicates Both Eyes.
- Sph / SPH (Sphere): Measures the lens power needed to correct myopia (minus sign –) or hyperopia (plus sign +). Measured in dioptres.
- Cyl / CYL (Cylinder): Indicates the lens power to correct astigmatism. Also measured in dioptres.
- Axis: A number between 0 and 180 degrees that specifies the orientation of astigmatism. Always accompanies the Cylinder.
- Add (Addition): Indicates the additional power needed for reading, used for presbyopia. Appears in progressive or bifocal lenses.
- Prism: Corrects alignment problems between the eyes. Less common, measured in prism dioptres.
How to Interpret Each Value in Your Prescription
1. OD and OS Rows
Your prescription is divided into two rows: the first for the Right Eye (OD) and the second for the Left Eye (OS).
2. Sphere (SPH)
This is the first important number. A minus sign (–) indicates myopia (difficulty seeing far), while a plus sign (+) indicates hyperopia. The larger the number (regardless of sign), the greater the correction needed.
3. Cylinder (CYL) and Axis
If you have astigmatism, you’ll see values in these columns. CYL indicates the amount of astigmatism, and Axis indicates its orientation in degrees. If these columns are empty or show “PL” (plano), it means you have no astigmatism or it’s so mild it doesn’t need correction.
4. Addition (ADD)
If your prescription includes an “Add” value, it generally means you have presbyopia and need an additional power for near vision. This value is used in progressive or bifocal lenses.
5. Prism
Prism correction is prescribed when there are alignment problems between the eyes. If you don’t have this value in your prescription, you don’t need this type of correction.
Tips for Understanding Your Prescription
- Don’t worry if both eyes have different values — it’s very common.
- The higher the numbers, the stronger the prescription, but this doesn’t always mean the same vision quality.
- If you have any doubts, don’t hesitate to ask your optometrist — they will be happy to explain each value.
- Keep your prescription updated: it’s recommended to have an eye test every 1–2 years.
Ordering Your Lenses at CristalesGafas
Now that you know how to read your prescription, at CristalesGafas we make it easy for you to order your lenses online. Simply enter the values from your prescription on our website and our team of registered optometrists will take care of the rest, ensuring your lenses are perfectly adapted to your visual needs.