How to Measure your Pupillary Distance
What is Pupillary Distance?
During your routine eye exam, your ophthalmologist will measure your pupillary distance (PD). This is the distance between the centers of your pupils and can help determine where you’ll look through the lenses of your glasses. On average, adults have a PD of 54-74mm while kids have a PD of 43-58mm. Your ophthalmologist can help make sure this is accurate so you get the most out of your prescription glasses, but you can also take this measurement at home if you’re looking to order glasses online.
Why Is It Important?
Prescription lenses have an “optical center” which will be determined by your pupillary distance. An optical center is where you look through the lens of your glasses, so your PD should be as accurate as possible to make sure your glasses work the way they should.
How Do I Measure PD?
To measure your PD at home, you can follow these steps:
- Stand in front of a mirror at about 8 inches away
- Hold a ruler against your forehead
- Close your right eye and align the ruler’s 0mm mark with the center of your left pupil
- Look straight ahead, then close your left eye and open your right eye
- Note the mm mark that lines up with the center of your right pupil
In order to get the most accurate results, make sure to measure 3-4 times so that your results are consistent. You can also have a friend measure for you to make sure you get the same results.
What’s the Difference Between Single and Dual PD?
It’s important to know that there are two different types of PD you’ll be dealing with when you order your prescription lenses. The first is single PD, which is the total distance between the center of one pupil and the other. This can be indicated by either distance PD or near PD. Alternatively, dual PD is the measurement from the center of each pupil to the bridge of the nose. This usually has two numbers (32/30 for example) indicating each eye.
How do I calculate near PD?
Near PD is often used to order reading glasses. To find this number, you’ll subtract 3mm from your single PD measurement. Alternatively, you can subtract 1.5mm from each number if you’re using a dual PD measurement.
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Whether you’re looking for new frames or hoping to learn more about how to measure your PD at home, we can help. Visit our online shop or get in touch with our team by filling out our online form.