You've uploaded your prescription, received your new glasses, and everything seems fine until you glance at the paperwork supplied with your lenses.
But the numbers don't match.
The prescription you uploaded says one thing. The details supplied with your new lenses say something else.
Naturally, your first thought might be: *Have my lenses been made incorrectly?*
In most cases, the answer is no.
What's usually happened is that your prescription has been transposed.
What Is A Transposed Prescription?
A transposed prescription is simply another way of writing exactly the same optical correction.
Think of it like distance. Some countries use Celsius whilst others use Fahrenheit. The numbers are completely different, but the temperature itself hasn't changed.
A transposed prescription works in much the same way. The lens laboratory has simply rewritten your prescription in a different format. Although the numbers look different on paper, they still describe exactly the same visual correction.
Why Has My Prescription Been Changed?
The short answer is that it hasn't.
Different opticians, lens manufacturers and computer systems often prefer different prescription formats. When your lenses are ordered, the laboratory may automatically convert your prescription into the format their manufacturing equipment uses.
This process is known as **transposition**.
It's a routine part of lens manufacturing and happens every day throughout the optical industry. In fact, most people never realise it's happened because they never compare the lens paperwork to their original prescription.
But The Numbers Are Completely Different
This is the part that catches most people out.
When a prescription is transposed, some of the numbers can change quite dramatically. Values may increase, decrease, switch from positive to negative, or vice versa. At first glance, it can look as though you're comparing two completely different prescriptions.
In reality, you're looking at two different ways of describing exactly the same lens power.
How Can I Tell If My Lenses Are Correct?
The best test is often the simplest one.
- Can you see clearly?
- Do your glasses feel comfortable?
- Does your vision feel as you would expect?
If so, that's usually a very good sign that your lenses have been manufactured correctly.
Your eyes don't care whether a prescription is written in one format or another. They only care that the finished lenses provide the correct correction.
Of course, if something genuinely doesn't feel right, it's always worth getting in touch. But seeing different numbers on your lens paperwork isn't, by itself, a sign that anything has gone wrong.
The Bottom Line
If the prescription details supplied with your new lenses don't match the prescription you uploaded, don't panic.
In many cases, your prescription has simply been transposed by the lens laboratory into a different format. The numbers may look different, but the finished lenses still provide exactly the same correction.
Just like Celsius vs Fahrenheit, it's simply a different way of describing the same thing.
If you're ever unsure, feel free to get in touch. We'll be happy to explain what's happened and double-check the prescription supplied with your order.
Thanks for reading.