- Have you ever wondered why it is
that when you order a free-form, or a digital lens,
you send the lab this
and then three days later you get back this
(upbeat instrumental music)
The difference between the order that you send in
and the order you got back
is that the lens has now been compensated.
And what that means is that the lab has put the full
computing power of its digital surfacing equipment to work.
To create a lens that best matches
the prescription written in the as worn position.
What does that mean?
Let's dig into a bit and find out.
First we're talking about lens design here.
This is super, super important.
We're designing the lens
we're not designing the prescription.
We're not changing the prescription,
we're not overriding anything,
we're not playing with the prescription
we're playing with the lens design so that it fills
that prescription in the most accurate way.
In ordinary, day-to-day optical dispensing,
up until let's just throw the number out there 25 years ago,
you are familiar with monocular PDs,
you are familiar with taking fitting heights
for line bifocals, progressive lenses.
We never really took much account for
vertex depth or distance,
wrap and tilt.
Let's talk about where those things come into play
so that you go from those perfect numbers
to those weird numbers that you get.
So phoropter, is that tool that a doc or a practitioner uses
they put that thing in front of your face
there's a picture of it
and they dial and they switch and they throw levers
and you shed little sounds
and you're looking at the big a and the little e and the i
and you say yes one is better, two is better,
two is better, one is better.
If you stop and think about it, that phoropter
has to be the same everywhere that doctor goes.
The doctor may go to multiple practices,
they may work at one store one day, one store the other day,
different doctors use different lanes within a store,
sometimes those places have five or six exam rooms.
The phoropter has to be a standard.
You can't have a whole lot of parts and pieces
that you can move,
if you do then every docs gonna get something different
and you'd have literally chaos.
So the phoropter is fixed.
If you think about the phoropter
sitting in front of someone's eye,
it's neutral this way.
The phoropter doesn't tilt on this axis
in front of your eye.
If I'm looking down, here's my person
here's my forehead rest and I'm looking through
the phoropter, here's my eye chart down here,
it doesn't move this way,
it can't swivel this,
there's no wrap change here.
I can dial a little bit of vertex depth,
in that I can read, I can say
that this is 10, 13, 15 millimeters away.
Away from what?
Away from this perfect, beautiful glass lens
that's inside the phoropter.
This is the perfect world.
This is repeatable, this is...
A different doctor, a different phoropter
is going to get something extremely
close to the prescription
that lets the person see clearly.
PDs it can be adjusted for, it can be moved this way.
Fitting height doesn't play into this
because it's lining up perfectly in front of their eye.
Vertex can be dialed in, there's a little,
I shoulda drawn that in there, sorry.
There's my
forehead rest
and this could be 10, 12, 13, there's a dial here
tells me how far the front of my cornea is
to the front of this beautiful, perfect glass lens
that's inside the phoropter.
Wrap and tilt let's call it zero.
Perfect world.
So I like to say if we take the perfect world
then we subtract the real world
we end up with lens design.
Let's see where that comes from.
I have got super lens and in the perfect world
when we're thinking about that phoropter piece,
I've got the perfect glass lens
and it is this way perfectly straight,
it's not tilted in this way in any,
and the O.C. of that beautiful glass lens is
perfectly aligned with my pupil
and I'm looking out at the big a
and I say yes, number one is much clearer
and the practitioner writes
these numbers.
It's the perfect world.
Is there such a thing?
'Course not.
In the real world,
this lens can be tilted this way,
can be tilted this way.
Those movements, mathematically,
with formulas that you know
change the way that the power
of that lens is perceived.
My minus seven, minus 125, my minus 650 at point 50,
if I pull that lens it is the perfect lens,
it's glass, it's gorgeous, it's beautiful,
it measures perfectly on auto lens meter,
specifically minus seven, minus one and a quarter.
If I put that on at any point other than the distance
and the exact same position that it was
when it was in the phoropter,
my brain sees it different.
That's compensated prescription.
How does it see it different?
It sees it different depending on
how far away from my eye the lens is,
vertex distance.
It sees it different depending on how the lens is tilted,
retro, panto, neutral,
and it sees it differently depending on
how the lens is turned as far as face form or wrap.
I can calculate those.
If I take these
numbers right here
and I account for my vertex depth,
this may go up or down.
The closer or the further away that lens,
depending on it's plus or if it's minus,
and how much power it is,
my brain will see it as being weaker or stronger.
If I tilt this lens
this way I induce cylinder
in the 90th meridian.
If I wrap my lens around face form
I'm going to induce power along the 180 in that meridian.
So the computer jumps in, takes over,
accounts for vertex depth, accounts for wrap,
accounts for tilt and builds this lens
instead of being minus seven, minus 125 at 85
to the numbers that you see.
It's gotta do the same thing for this.
That 650 could be stronger, it could be weaker
depending on the power, minus, plus,
if it's moving away from the eye or moving in.
All that's covered on the website.
If I tilt the lens along the wrap,
the zero, 180, looking above,
it's gonna change the power.
If I tilt the lens
my panto, retro, this way,
it's gonna change the power.
It's gonna change the power, it's gonna change the power.
It will even alter the perceived position of the axis.
Our super computing power
let's us recalculate those three
so that you go from this to that wild and crazy,
to the thousandth of a diopter, excuse me,
hundredth of a diopter now, prescription where
this different, this is different and this is different.
We did not change the prescription.
We changed the lens,
so that when the person puts on that pair of glasses
that they chose and it's got tilt
and it's got wrap and it's got vertex distance,
that when they put them on,
when they're looking through that lens,
they get this up here.
The lens itself,
put it in the lens meter,
try to read it, you're not gonna get this.
But in the wearer's brain
they're getting this
because we've compensated the lens, powers, position,
degrees, axes, to be correct for the as worn position.
That is what compensated prescriptions are all about.
Thank you so much for watching!
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