How To Measure Your PD (and Other FAQs About Online Glasses)
Lately, I’ve been seeing a lot of ads for new online glasses, so I decided to do a deep dive into the most frequently asked questions.
What is my PD?
PD stands for pupillary distance. It is the distance between your pupils. This is measured when glasses are being made to help ensure that your lenses are properly centered over your eyes (which is not always the center of the frame!)
How can I measure my PD?
Firstly – this measurement is important because if your lenses are off center, it can cause distortions and lead to eyestrain and headaches.
Second – there are lots of suggestions online on how to guesstimate it yourself in various ways, like looking at yourself in the mirror, asking a friend, or using an app and a credit card. These methods are flawed, and this study found that regular people attempting to measure their PD using techniques available on the internet resulted in poor accuracy https://pubmed.ncbi.nlm.nih.gov/22581116/ (Disclaimer: I was involved in this study!). There were some people who managed to guess pretty close to their actual measurement, but a lot were not even close. Even if you were one of the people got close, you wouldn’t know for sure without being able to check somehow.
If I asked you to find out the length of a piece of wood, a few people may be able to get pretty close by estimating with their hands or something, but you would never be really sure until you find someone with a proper measurement device!
My glasses are giving me a headache. How do I know if the lenses are correct?
That is the risk with buying online. Being able to trust that the person did their job properly in measuring you, making the glasses, and verifying that the glasses were made according to the prescription is part of the service you’re paying for. Glasses are classified as medical devices, so optometrists and opticians have standards that they must follow, and they are held accountable by their respective Colleges. There is no oversight with online glasses.
There are many factors affecting your comfort in glasses, aside from just the prescription – there’s the PD, optical center height, lens material, lens curve, coatings, and proper frame fitting…. In a study of 154 pairs of glasses ordered online, 28.6% failed tolerance standards for at least 1 parameter (for example, wrong lens types, lens treatments added or omitted), and 22.7% failed impact testing. This means nearly half of them failed on some optical criteria or safety requirements! (https://pubmed.ncbi.nlm.nih.gov/21871395/)
Why won’t my optometrist give me my PD?!
It is not the optometrist’s job to measure your PD. It is not part of a regular eye exam, because there is no medical value for it outside of buying glasses. Whoever is selling you the glasses should measure it. Online companies have offloaded that responsibility to you, which is partly how they keep their costs low, and as a result, they don’t need to be held accountable if you do it wrong. 🤷🏻♀️
I read that most frames are just made by one company! There’s a crazy markup on glasses!
It’s true that frame companies spend lots of money on branding and marketing. Like any other product, if you want a designer frame, that is going to cost a lot more than start-up online frames. I want you to understand how to find quality eyewear, but after a certain level, the difference becomes more about branding, with smaller differences in quality/style. In my daily life, I don’t walk around in designer clothes. I can notice the difference between a polyester T-shirt that makes me sweaty vs a breathable cotton shirt, and there’s a difference when the seams are off center vs when they’re cut properly, but after a certain point when you have quality materials, the differences in a T-shirt just become related to style (do I want it to be boxy or have a defined waist? Different sleeve lengths, size of the arm holes, etc…). You will pay more for recognizable, household brand names which spend millions on convincing you that their product is higher end.
We have those frames, but we also have lesser known brands which are still good quality with modern styles, and we back them with our same great warranty! It doesn’t have to just be either cheap $10 online glasses or $500 boutique glasses – there is a middle ground!
Spoiler alert: Regardless of whether you choose a designer frame or one of our up-and-coming brands, we still use quality lens materials and coatings. To keep within a budget, some places may compromise on your lenses to make up for the cost of the frame. Since we are not a retail store, our prices are not structured this way.
Which brings me to the next question…
What kind of lenses should I get?
Some companies are not transparent (😉) about what is their “standard” lens. Sometimes they use polycarbonate, which has more chromatic aberration (a type of distortion) than other lens materials, so images can appear less sharp. It’s also more prone to scratches. They may charge you extra with the promise that it’ll make the lenses thinner. Our opticians would be able to guide you on whether this would make a noticeable difference for your individual prescription to outweigh some of the cons, and help you find the appropriate lens material to suit your needs. We do, however, often use it for kids’ glasses since it is more impact resistant.
Our lenses come with an anti-scratch coating, and I would recommend anti-reflective coating and UV protection as well. This way you will be protected from UV, even without sunglasses (though you might still squint in bright sunlight without a tint)! See this post to learn more about anti-reflective coating.
Will this frame fit me? I read that I can just use the numbers from my current glasses to find the same size.
Look at these two shirts. Both of them have “sleeve length” of 50cm. Will they both fit me the same way? 🤔
No problem, I can upload a photo of myself to “try on” the glasses!
Great, that is such a neat tool! How does this sweater look on me?
I’m being facetious, but I hope you can appreciate how virtual “try-on” programs are not at all the same as actually trying them on. Furthermore, some measurements, such as the optical center height, varies a lot depending on how the frame sits on your face.
In the end, online eyewear companies are started by various business and marketing people who are applauded for the ability to make money. Optometrists have a code of ethics by which they pledge to abide, and there is a path of recourse – you don’t have to be left wondering whether you actually received what you ordered.
Think about buying a helmet for your child – do you want to buy from a reputable company who has a legal obligation to follow safety standards, or someone who has a decorated resume for success in maximizing profits? 🤔
My beef is not with new, fresh, startup eyewear brands, because more diverse frame selection benefits everyone! The problem is when the process – self measurements, virtual eye tests, lack of prescription verification – compromises patient care.
We have top service and a great selection at Whitbyvision.ca, but if you are not local, I recommend that you seek to purchase your glasses and contacts from a licensed professional.
Stay tuned for my next post about blue light glasses! and Progressive lenses! There is so much to think about when it comes to choosing glasses 😰