Why retailers are asking you to measure your own PD

When shopping for glasses online, you've probably seen websites encouraging you to measure your own pupillary distance (PD). They might provide tutorials, printable rulers, or smartphone apps, suggesting it's a simple DIY task. But why do they promote this potentially risky practice? Let's uncover the real reasons behind this concerning trend.

Quick Summary (TL;DR)

• Online retailers are incentivized to downplay the importance of an accurate PD.
• Self-measurement is good for them, bad for you.
• An accurate PD is needed for your prescription to be effective.
• An eye care professional is your best bet to get the vision you're paying for.

The Business Model Behind DIY PD measurements

Why Retailers Promote It

1. Cost Reduction

Online retailers know that there is a good chance your eye doctor did not include your pupillary distance measurement with your prescription. But these retailers cannot make you glasses without this measurement!

What could they do? They could find a way to have their own professionals measure your pupillary distance. But let's face it, they wouldn't be able to provide the very low prices they provide if they had to build out locations, staff them, and operate them to do this. They could coordinate with existing professionals, but there is a conflict of interest there! Most eye doctor offices are integrated with an optical store so that they can be a one-stop shop for your vision needs. Even though they need your eye doctor's prescription, they are also competing with them!

So that leaves us with what actually happens. That's the cheapest option, as you'll do this for free. They might point you to a free app or even a printable ruler to help you. But at the end of the day, if the measurement is incorrect, it's on you. But it may not be obvious right away that you're not getting the vision correction that you were meant to get. At the end of the day, when cost is reduced, someone pays the price, and in this case, it's you!

2. Better Sales Conversion

Many customers don't find out there's a measurement missing from their prescription until they are filling out the little boxes on the prescription page of an online eyewear website. Maybe this happened to you. At this point, you are what's known in e-commerce terms as a high-intent user. But, if you don't have your PD, then you won't complete the purchase then and there, and this is bad news for that online retailer. They could suggest you call your eye doctor and see if they have the number on file and give it to you. If that doesn't work, the next suggestion might be to go somewhere in person to have your PD measured for free or for a small fee.

This isn't great for them, because there's no guarantee you'll come back to your cart. They know that the more time that passes, the less likely you are to complete the purchase. They know, had you had your PD, you would have clicked "BUY" then and there. This is why every online retailer has a page instructing you on how to measure your PD yourself, with no discussions on the pitfalls or drawbacks. Better to have you complete the purchase right away than do the right thing and risk losing your purchase.

The Marketing Tactics

They Make It Sound Easy

1. Many Options Are Suggested

Many different options are suggested, sometimes by the same retailer and even on the same page. What's very troublesome is that often all these options are presented with no discussions of which have the best chance of getting a measurement that close. While none is as good as a professional measurement, some have a better chance of getting you in the ballpark than others. But we seldom see online retailers making distinctions between the different methodologies. Here are some of the things we've seen being suggested online.

• Using a millimeter ruler and a mirror.
• Using a millimeter ruler with the help of a friend.
• The credit card selfie with a smartphone or a web-based app.
• Smartphone apps, or websites that use the webcam.
• Printable rulers.
• Taking a selfie with a ruler and then using a photo editor to transfer the measure.
• Using an old pair of glasses and marking dots on them.
• Guessing based on age and/or ethnicity and gender.
• Using Virtual Reality Headset settings.
• Eyeballing it (sorry what!?)

2. Technology Appeal

Who doesn't like doing new things with their fancy smartphones? Several smartphone apps exist to use the phone's existing camera to measure pupillary distance. Many of them work quite differently from each other. But also, so do the phones! Every phone camera is a bit different, from model to model, and will have different distortions. Have you ever taken a selfie that's just a little too high or a little low and felt your face's proportions was grossly distorted? Yep! Well, these distortions exist in every image, but they are noticeable at a small scale. No one designed a cell phone camera to take millimeter-accurate measurements!

Many studies have shown that all the different apps vary in their accuracy and measurements. They also vary in the instructions given to the user and the fail-safe and correction steps that exist to help improve accuracy. Figuring out what is the best app to use is surely more work than going to see a professional!

What They Don't Tell You

1. Accuracy Issues

As mentioned above, online retailers don't tell you how your self-measured PD may deviate from its actual measurement. They have no incentive to, their instructions solely to allow you to complete your purchase as soon as possible. Most people who measure PD themselves, or even with a friend, feel uneasy about it. They might take several measurements and take an average. Or try several methods and average those. Maybe that's a sign that something is not quite right?

2. Health Risks

The downsides of ending up with glasses with the wrong PD are not discussed. This could lead to eye strain, headaches and suboptimal vision. In the end, with the wrong PD, you are not getting the vision you have been prescribed. Why take a chance?

3. The Hassle

If you don't have the right PD, but are lucky to know it right away, you'll still be paying for it with the inconvenience. Granted, many online retailers have great return policies. But some like to play games or add extra steps in the hope that you won't complete them before the return window closes. You'll likely have to go back to your old glasses for 2 or 3 weeks while a new pair is made. Hopefully they start making them before they receive the old ones in the mail, or it could take even longer. And, look, you still need to get your actual PD!

It's not just about PD

Here's what the online retailers won't tell you. For some people, even an accurate PD isn't enough - there are other measurements required to optimally align the optical center of the lenses with your pupil. There are no apps or websites that can make that call for you. Find a PD-friendly practice today!

Remember: Your vision health is too important to risk with DIY measurements. Don't let retailer convenience override your need for accurate, professional care.

Ready to get the perfect glasses? Use our free search tool to find an optometrist near you who will provide the PD you need!