Is my eyesight that bad? How to understand your glasses prescription

When you go to your annual eye exam, you may be curious about how the optometrist diagnoses your eyes, leading to a different fitting by an optician than you had before.

Whether or not your eyesight changes from year to year or remains the same, it can be difficult to make sense of your prescription — especially if you choose to order lenses online.

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If you'd like to better understand how to read the remedy for your eyesight, vision care health insurance company VSP has some pointers.

First, there’s “OD” and “OS.”

OD is the prescription for your right eye.

OS is the prescription for your left eye.

Below is an example of what an eye prescription will look like.

OD -4.00 -1.50 x 180

OS +.50

To understand the numbers, know that they reflect refractive power, astigmatism and the axis of your lens.

Refractive power is the first number in the series. It denotes how nearsighted (you can see close objects clearly but distant objects are blurry) or farsighted (you can see objects in the distance is clearly but close ones are blurry) you are. Nearsightedness is indicated by a minus sign while farsightedness is marked by a plus sign. The refractive power is your spherical correction based on your sight.

Astigmatism is the second number, which can be written with a plus or minus sign. The number is your cylindrical correction and notes how well or how poorly light is focused onto the retina by the eye.

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The axis is the third number and indicates the direction of your astigmatism. If the axis is 180 degrees, the astigmatism is horizontal.

If neither the second or third number (astigmatism or axis) are present in your prescription, it’s likely you don’t have astigmatism, a common condition in which the curve of the eye is irregular.

DV or NV may also be included in your prescription. DV is distance vision and NV is near vision. DV corrects the ability to see things far away while NV notes your prescription is strictly for reading.

It's also common for people to have different prescriptions for different eyes. The prescriptions also shift because people's eyes change, according to Medical News Today. While children's eyes change more frequently since they're growing, adults' eyes don't remain the same, either. They simply change more slowly.

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As you age, you should be more aware of potential eye conditions that can impact you, including cataracts, glaucoma and age-related macular degeneration, which the National Institutes of Health says is the leading cause of blindness in people over 65.

If you have any concerns about your eye prescription, contact a medical professional, such as an ophthalmologist.