Something might be missing if you decided to take the prescription from your last vision exam and shop online for glasses. The website you chose to order glasses from will ask for your pupillary distance (PD). This measurement is critical for ensuring the lenses in your new glasses line up correctly with your eyes in order to improve your vision.
If you’re new to buying glasses online, you probably didn’t know to get your pupillary distance measurement from your eye doctor while you were there. Since this is a pretty common scenario, people have invented some. . . creative ways to come up with this measurement for themselves.
One Ruler to Rule Them All
Step one: get out your millimeter ruler. What do you mean you haven’t touched one of those since middle school and that math problem about the triangles? Fine. Step zero: go buy a millimeter ruler. You could print one out online as well, just make sure your printer is set to “actual size.”
Anyway, now that you have your millimeter ruler (or piece of paper) in hand, you also need a friend. Hopefully you’ve gotten one of these more recently than that ruler you used in math class. Have them stand about an arm’s length away from you.
Then, they need to measure the distance between your pupils. For best results, they should be wearing their own glasses so they can eyeball (no pun intended) where exactly the ruler starts, right at the center of one pupil, and read the measurement directly at the center of the other pupil. Ideally, they are holding the ruler (or paper) perfectly still over the bridge of your nose as this is being read. Holding your breath might help with this. As they do this, focus your eyes on some spot about 10 feet off in the distance. Staring directly at your friend might creep them out and will mess up your measurement.
Repeat this about three times and average them out to account for either (or both) of you moving. If you’re concerned about the accuracy but don’t want to give up on your online glasses shopping experience yet, there is another way you can try.
Mirror Mirror on the Wall
If you’re more of a lone wolf type, you can actually measure your own pupillary distance, no friend required. You just need to replace “friend” with “mirror.” While balancing the ruler on the bridge of your nose, stand about arm’s length away from the mirror and read the measurement.
What if you can’t see yourself at arm’s length in order to read the ruler (let alone those tiny numbers)? After all, you are doing this in order to purchase a pair of glasses.
Luckily, poor eyesight isn’t an excuse to not know your pupillary distance. You just need a highlighter as well. This time, look at yourself in the mirror and use the highlighter to dot where your pupils are on the lenses of your glasses. Then, you can take the glasses off and read the measurement by putting the ruler as close to your eyes as you need.
So, how to clean highlighter off your lenses? You did use an old pair of glasses, right? Oh well, you’re shopping for new ones anyway.
Or Just Use Technology?
However, the desire for people to measure their own pupillary distance has also resulted in some successful and simple methods as well. There are various ways which use technology to create an objective measurement. Unsurprisingly, measuring your own pupillary distance with the assistance of technology turns out to be both more accurate and way easier than relying on a combination of a friend, mirror, and millimeter ruler.
At the rate technology is advancing in this area, there might be even easier methods of measuring your pupillary distance right on the horizon.
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by Joyce Handzo
If you’ve ever tried to purchase glasses online, you’ve come across the term “pupillary distance.” How is this important for your vision and why do you need it to buy glasses?
Pupillary distance is another measurement which is required to make sure your new prescription eyeglasses fit and correct your vision properly. In order for the lenses to do their job, they need to be centered over your eyes. If it is done right, your pupil will be correctly aligned with the lens.
What the lens is really doing is redirecting the light that is coming into your eye so it focuses directly on the retina. When the lens is fit to your pupil, the incoming light is centered which allows your vision to be corrected optimally. Properly-fitted lenses with an up-to-date prescription are important for both seeing well and preventing eyestrain.
This is why some people opt for prescription reading glasses as well. The ones available off the shelf at a store are meant to be one size fits all and don’t take a person’s pupillary distance into account.
Although it is important for fitting eyeglasses, it is not always included on the prescription from your eye doctor. You may have to ask specifically for this, especially if your heart is set on a unique pair of glasses you found online. If it is on your prescription, it’s usually marked as “PD” followed by a number, such as 60. When buying glasses and lenses from a retail store, they will measure this for you after you pick out your pair.
But don’t worry if you don’t see it on your prescription. Pupillary distance is measured in millimeters and is simple to find out your own. Thanks to advancing technology, you even have some options for measuring your pupillary distance.
The traditional way would be to use a ruler with millimeter markings. With this method, you need to hold the ruler on the bridge of your nose and measure the distance between the center of one pupil to the center of the other. You do need either a mirror or a friend to help you read the measurement. It is suggested to do this a few times in order to correct for any variations or errors you (or your friend) might have made.
But if you’re nervous about making a mistake because you can’t read the tiny numbers on the ruler or your hand is unsteady, you have another option. With access to a Smart Vision Labs vision test, you can get these results without worrying about your own accuracy in measuring.
In this test, you use a “card” that has black dots over a white background, like a polka dot pattern. You hold this under your nose while aligning yourself with the screen on the exam (see video). The technology can detect the presence of the card and will then direct your position, such as if you are too close to the screen. After it recognizes the card and your eyes, it will take a few seconds to analyze the image and tell you what your pupillary distance is. You then have the option to save your results or redo the test.
A pupillary distance measurement is necessary for properly fitting your eyeglass lenses. There is no reason to walk around with inaccurate glasses when it is so easy to get this number. Be sure to take your number, and the rest of your prescription, the next time you shop online for trendy eyeglasses.