If you wear glasses, understanding your eyewear prescription is important to ensure that you can see clearly and comfortably. Your prescription is a written order from your eye doctor that includes specific measurements and information about your eyesight. In this blog, we'll go over what each part of your eyewear prescription means and how to read it.
OD and OS
Your prescription will start with "OD" and "OS," which stand for "oculus dexter" and "oculus sinister," respectively. These terms refer to your right eye and left eye. Your prescription will have a separate set of measurements for each eye.
Sphere, Cylinder, and Axis
The next set of numbers on your prescription represent the measurements of your eyesight. The "sphere" measurement indicates how nearsighted or farsighted you are. A negative number indicates nearsightedness, while a positive number indicates farsightedness. The larger the number, the more severe your nearsightedness or farsightedness.
The "cylinder" measurement is only included for people with astigmatism, which is a condition that causes blurry vision due to an irregularly shaped cornea. The cylinder measurement indicates the degree of astigmatism. A higher number indicates a more severe case of astigmatism.
The "axis" measurement is also only included for people with astigmatism. It indicates the angle at which the astigmatism is present in your eye.
Add and Near PD
If you need bifocal or progressive lenses, your prescription will include an "add" measurement. This measurement indicates how much additional magnification is needed for close-up work, such as reading or computer use.
Your prescription may also include a "near PD" measurement, which is the distance between your pupils when you're looking at something up close. This measurement is important for making sure that the bifocal or progressive lenses are positioned correctly.
Reading Your Prescription
When you read your prescription, you'll see a series of numbers and abbreviations that may look confusing at first. Here's an example of what a prescription might look like:
OD: -2.50 -1.00 x 180 OS: -3.00 -0.75 x 175 Add: +2.25
In this example, the right eye (OD) has a sphere measurement of -2.50, a cylinder measurement of -1.00, and an axis measurement of 180. The left eye (OS) has a sphere measurement of -3.00, a cylinder measurement of -0.75, and an axis measurement of 175. The add measurement is +2.25.
If you're having trouble understanding your prescription, don't hesitate to ask your eye doctor for help. They can explain each part of your prescription and answer any questions you may have. Remember, understanding your eyewear prescription is an important step in maintaining good eye health and clear vision.