Key Takeaways
- OD means your right eye, OS means your left eye, and OU means both eyes together.
- A minus sign can indicate that you’re nearsighted, while a plus sign can indicate that you’re farsighted.
- SPH, CYL, and axis work together to shape your lenses for clear vision.
- The add number gives extra power for reading and close-up work.
- A higher number means a stronger lens, so 1.50 is stronger than 1.25.
Maybe one of our eye doctors at Island Eyecare just handed you your new glasses prescription, and you’re looking at it feeling a little confused. It’s a small slip of paper covered in numbers and letters, and it sort of looks like a puzzle. Our team wants to help you understand what those numbers mean so that you can have a better understanding of your unique eyes.
Your glasses prescription is a set of measurements found during a comprehensive eye exam that tells a lens maker exactly how to shape each lens so your blurry or strained vision turns sharp again. Each eye gets its own row of numbers because your two eyes rarely have exactly the same prescription.
What Do OD and OS Mean on Your Prescription?
The first thing you might notice is a pair of short letters. OD indicates your right eye, while OS means your left eye. These come from older Latin terms, but you only need to remember which eye is which. Sometimes you’ll see OU, which means both eyes together.
So when you look at your prescription, the OD line tells the lens maker how to build the lens for your right eye, and the OS line does the same for your left. Reading across each row gives you the full picture for that eye.
How to Read the SPH, CYL and Axis Numbers
These three numbers are usually split into columns, and they indicate how the lens should be bent in order to correct the light entering your eye. These numbers help your vision go from blurry to clear.
Sphere
The sphere number shows how much lens power you need to see clearly. A minus sign can indicate that you’re nearsighted, which is when distant objects like road signs look blurry. A plus sign can indicate you’re farsighted, meaning nearby objects may be harder to see.
The bigger the number, the stronger the lens power. A reading of -3.00 needs more correction than -1.00.
Cylinder and Axis
The cylinder number is designed to correct astigmatism, which occurs when the shape of the front of your eye is slightly irregular. With astigmatism, your cornea (the clear outer layer of your eye) is shaped more like a football than a basketball, which can make things look blurry at any distance. If the CYL box is empty, that simply means your eyes don’t need astigmatism correction.
The axis measurement indicates the orientation of the astigmatism correction. It tells the lens maker where to position the CYL correction in the lens. If you don’t notice an axis measurement, it’s because you don’t have an astigmatism to correct.
What Add, Prism, and Base Mean for Your Lenses
Everyone’s eyes are different, so not all prescriptions look the same. The add, prism, and base measurements are for certain types of eye issues, so you might not see these on your prescription at all.
Add for Reading
The add number gives you extra power for close-up vision. This type of correction is often prescribed to those managing presbyopia, an age-related vision change that impacts the ability to see up-close objects. This number can help shape bifocals or progressive lenses, so you can read a book and then glance up to see across the room without swapping glasses.
Prism and Base
Having a prism measurement on your lenses is less common. This type of prescription can help those with strabismus, which happens when the eyes don’t line up quite right.
The base measurement tells the lens maker where the prism sits, such as up, down, in, or out. If these boxes are blank, your eyes are teaming up just fine on their own.
Common Questions About Your Prescription Numbers
A few questions come up again and again, so here are quick answers you can keep in mind.
- Is +0.25 nearsighted or farsighted? The plus sign indicates that you are farsighted. Even a small plus number leans that way, though +0.25 is a very mild amount.
- Is 1.25 or 1.50 stronger? The 1.50 is stronger because a higher number indicates greater lens power, whether the sign in front is plus or minus.
- When should you book an eye exam? Though everyone is different, it’s often recommended that healthy adults have an eye exam every year, or if you feel your glasses are no longer correcting your blurry vision.
Schedule Your Appointment
Whether you’re looking for a pair of frames you’ll love wearing, or want to check on your visual health, our team at Island Eyecare would love to see you. Book your eye exam today and see Sydney a little more clearly.
