How remote measurements actually work — and why, in most cases, you don’t need to measure anything yourself
Getting prescription lenses measured online worries most people before they order: if nobody’s sitting in front of you with a ruler, how can the measurements possibly be right?
It’s a fair worry, and it’s worth answering properly. The short version is that reglazing works differently from buying a complete pair of glasses online. We’ll have your actual frame in our hands, and in most cases we have your existing lenses too — which means the measurements come from the glasses you’ve already been wearing, not from a guess.
What Measurements Do Prescription Lenses Actually Need?
Two things matter beyond the prescription itself.
Pupillary distance (PD) is the distance between the centres of your pupils. It tells us where the optical centre of each lens needs to sit so you’re looking through the right part of it. Worth knowing: the PD is not part of your prescription, which is why it has to be obtained separately.
Vertical heights tell us how high in the frame that centre should sit — which matters when a lens has more than one viewing zone, or when the lens is thin enough that being slightly off is noticeable. Note: the vertical fitting height does differ from frame to frame based on the dimensions as well as nose bridge design.
What we need depends on what you’re ordering:
- Single vision lenses — PD only
- Multifocal (Varifocal, Bifocal, Occupational) — PD and vertical heights
Five Ways We Get Prescription Lenses Measured Online
There isn’t one method — there are five, and you pick whichever suits you:
- From the lenses already in your frame. If your current lenses work for you, we measure them directly.
- From a spare pair you send in. Age doesn’t matter. If they were comfortable at the time, the measurements are usable.
- You tell us. Many opticians give you your PD, and you may already have it from a previous order.
- A photo of you wearing your glasses, taken before you post them to us.
- A photo wearing a different pair, holding a credit-card-sized card to your forehead. Our measuring software uses the card — a known, fixed size — to bring the image to scale, then reads both your PD and your vertical heights from it.
That last one sounds improvised, and it isn’t. Scaling from a reference object of known dimensions is a standard optical technique, and it’s precise.
How Accurate Is This, Really?
So how accurate are prescription lenses measured online, really? This is the part people are sceptical about, so here’s the honest answer.
We process thousands of orders every month using exactly these methods, and visual problems traced back to measurements are rare. The reason is straightforward: in most cases we’re not estimating anything. We’re reading measurements off lenses that already sat in front of your eyes and worked.
Where a photo is used instead, the scaling reference removes the guesswork — the card fixes the scale, and the software does the rest.
What You Actually Have to Do
Less than you’d think.
- Place your order and upload your prescription in the ordering wizard
- A few minutes later you’ll get an email asking how you’d like your measurements taken
- Choose one of the five options above
- If you choose from the lenses in my frame or from a spare pair — you’re done. Post your glasses and leave the rest to us.
Only the photo options ask anything further of you, and that’s a phone camera and two minutes.
We Check Everything Before We Glaze
Your glasses go through a verification stage — usually the same day they arrive with us.
We check the frame itself, and we check that the prescription you’ve sent is valid and complete for the lenses you’ve ordered. If you’ve paid for varifocals, for example, the prescription needs to include a reading addition. If something’s missing or doesn’t look right, we get in touch before anything is cut. Nothing gets glazed on the strength of an assumption.
If you’re unsure whether your prescription or your frames will work, send them and we’ll tell you.
