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Picking out contact lenses should be easy, but the prescription can look like a secret code. SPH, CYL, AXIS… what does it all mean? Don’t worry, we’re here to help you crack the code. Understanding your prescription is simpler than you think. Let’s break down the key terms so you can confidently order the right lenses for your eyes.
OD and OS: Which Eye is Which?
This is the first thing you will see on your prescription. It’s simply a way of telling your right eye from your left.
- OD stands for “oculus dexter,” which is Latin for right eye.
- OS stands for “oculus sinister,” which is Latin for left eye.
Sometimes, you might also see OU, which means “oculus uterque,” or both eyes.
SPH: The Power of Your Lens
SPH stands for Sphere. This number indicates the main power of your lens. It corrects for nearsightedness or farsightedness.
- If the number has a minus sign (–), you are nearsighted. This means you can see things up close, but not far away.
- If the number has a plus sign (+), you are farsighted. This means you can see things far away, but not up close.
The larger the number, the stronger the correction you need.
CYL and AXIS: Correcting Astigmatism
If you have astigmatism, you will see these two numbers on your prescription. Astigmatism means your cornea is shaped more like a football than a perfect sphere, which causes blurry vision.
- CYL is the Cylinder number. It measures the severity of your astigmatism. Like SPH, it will have a minus sign and will be a value like -0.75 or -1.50.
- AXIS tells your doctor where the astigmatism is on your eye. It is measured in degrees, from 0 to 180.
If your prescription does not have these numbers, you do not have astigmatism that needs to be corrected by your contact lenses.
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Other Important Terms
You might see a few other abbreviations on your prescription.
- ADD stands for Addition. It is used for bifocal or multifocal lenses to correct for presbyopia (the natural loss of close-up vision as we age).
- BC This is the Base Curve. It measures the curvature of the back surface of your contact lens. It is crucial for a comfortable fit.
- DIA is the Diameter. It measures the width of the lens. This also ensures a proper and comfortable fit on your eye.
Need to Renew Your Prescription?
Don’t let an expired prescription stop you from getting the contacts you need. Lens.com offers a convenient online eye exam that lets you renew your prescription from the comfort of your home. It’s a quick and easy way to get a valid prescription and continue ordering your favorite lenses.
One Last Important Note
Your contact lens prescription is different from your eyeglass prescription. They are not interchangeable. This is because eyeglasses sit away from your eyes, while contacts sit directly on them. It is important to always use a current and valid contact lens prescription when you order from Lens.com.
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