Pupillary Distance: Why You Need It and How to Get It - Smart Vision Labs

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.

Related Posts
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Why Eyeglasses Require Prescriptions
All I Want are Glasses—Not an Eye Exam!

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