- Ah, there.
That's better.
(upbeat music)
Hello and as always, I'd like to welcome you
to the Laramy-K Optician Works Training Center.
Today we are gonna work through three examples
of basic single vision decentration calculations
and the blocking procedures.
We will work through the numbers
demonstrated on the whiteboard
and then I'll show you what it would actually look like
in the simple manual blocker.
These are extremely common powers.
Common PEs and frame sizes.
These are jobs you might well run
five, 10, heck even 15 times a day as a working optician.
Fear not, that is what this video series is all about.
For this example, we will have a right of
a minus one sphere,
a left of a minus two sphere
a customer PD of 58,
and a frame with the measurements of 54/19.
Let's get goin'.
All right, for those of you who saw part one
and that better be you,
you may have noticed that I had to change Superframe.
I had to make Superframe a little smaller.
I think it turned out quite well,
I think we'll call this version two,
I think there's a version three in the works.
I did keep the rhinestones, in case you were worried.
The reason I had to shrink Superframe down a little bit,
is because even when I use gigantic Superlens,
when I decentered it you may have noticed
when I moved it over that I ended up with a gap over here.
That would mean that I literally didn't
have enough lens there to cut out
and make a pair of glasses.
It's a really bad thing, we'll get to that
in another video.
How do I come up with my frame PD of 73?
Again, I'm not gonna go into a whole lot
of detail here, there's an excellent video
on the boxing system and of course
there's tons of that stuff on the website.
But the short answer is
if I add my frame A and my DBL
A and my DBL
that matches the geometric center of the eyewire openings
because there's nothing to measure here,
measuring across is a little bit more
accurate way of doing it.
This particular frame has a boxing
frame measurement of 54/19.
54 added to 19,
nine, three, carry the one, is 73.
With powers like these,
if you simply used the boxing system numbers on the frame,
nobody is going to die.
Everything will be just fine.
But, we have our 73.
Our human, the person that's actually
going to put on and wear this pair of glasses,
the distance between the centers
of their pupils is 58 millimeters.
Their eyes are closer in than the centers of the frame.
If I have got a frame PD of 73 and I take away my 58,
why am I using a calculator?
Because my brain doesn't work very well.
And you know what?
The lens that I put in here, hey,
it could be $75 or more and I don't wanna make a mistake.
So, that gives me 15
and I have two eyes so I go 15 divided by two,
so I get seven and a half millimeters
in decentration for each of my eyes.
When I finish this pair of glasses,
I need the center dot from my lens meter
the OC mark on my lens
to move from the center of that frame over,
decentered in and placed directly in front of my pupil
which is seven and a half millimeters
closer in towards the nose.
That's where those numbers come from.
I'm gonna take this one and I'm gonna move it over
seven and a half millimeters for a total
decentration of 15.
Here is what it would look like in the blocker.
Well, here is my manual blocker.
I'm gonna start as always with my right lens
and my decentration amount is seven and a half.
That's zero.
That's five.
That's six,
seven and a half.
I'm gonna take my right lens.
That would be zero.
Gonna move that center dot over
to line up with that seven and a half mark.
I'm gonna load a block in the blocker.
Steady the lens,
bring that around,
stick it to the front of the lens,
and I'm good to go.
If I turn this lens over and I look,
that would be the center of my frame
and my OC has been pushed over towards the nasal
as if I were wearing this lens
in a pair of glasses further right.
One down, one to go.
Five, six, seven, and a half.
We load a block.
Take my left for indecentration,
right moves right, left moves left.
That looks great.
Stick my block on.
If I turn this over, there's the center
of my eyewire opening, there's my OC,
left eye decentered in towards my nose
as if I was wearing this.
Ready for example number two.
We'll have a plus one in the right,
a plus one fifty in the left,
customer PD of 62,
frame measurements of 60/19.
What is my frame PD?
My A, my DBL, my A is 60, my DBL is 19.
Needs a pretty big frame.
The A opening is quite large.
The distance between our two lenses is pretty big.
I have a frame PD of 79 millimeters.
A big man's frame, or one of those
horrible sunglasses that are out now.
Its boxing system measurement would be 60 box 19.
With powers like this of plus one and plus one fifty.
If you chose to use your boxing system,
instead of taking out and doing it
like you're supposed to, no one would die.
If I have my frame PD of 79,
my human PD of 62,
79 minus 62,
I have a difference of 17.
17 divided by two
is eight and a half millimeters in decentration per eye.
When I do the finishing work,
I am going to take my lens
and I need to move my center OC dot.
My two outer ones are only used
when I have a lens with a cylinder amount.
I can take my center dot and I need to move it
from center of my eyewire opening
eight and a half millimeters in,
eight and a half millimeters in.
When I show you this on the block in a second,
my OC's gonna be over here
and my block is going to be placed here.
One of the reasons that this second part
of the series is baby steps is
we're only working in the horizontal.
We don't have enough power to worry
about doing an OC height or moving this way.
So that's why we're doing baby steps.
Let's see what that would look like in the blocker.
For example two, I have eight and a half
millimeters of decentration.
That would be zero.
That would be five, six, seven, eight
and a half.
Load up a block.
Grab my right lens.
Decenter that OC eight and a half over.
The two outer dots, I can use them
as a good reference point.
It's a spherical prescription so
they aren't necessary but it's always good
to keep things in line.
Open that.
Stick that block on.
Sure enough, there would be the opening of my frame.
There's my OC shifted nasally in my right.
Let's do the same for the left.
That's five, six, seven, eight and a half.
Beautiful.
Let's stick a block in there.
Take my left.
That would be on center zero, I'm moving it over,
by eight and a half.
Beautiful.
Stick my block on.
Sure enough, there would be the center
of my eyewire opening and there's
my OC shifted nasally in my left.
For example three we have a right
of minus one seventy five,
a left of minus point seven five,
PD of 64 and a frame measuring 52/17.
It was just this morning that I put up part one
on the YouTube channel.
And I get feedback from people quite a bit, thank you,
and it was overwhelming that people said
that when they understood this
and looked at it and took the lens and looked it over,
for most people it didn't have that much to do
with finishing or finishing layout
it had to do with inch thickness
and the relationship between PD and frame size.
All I can say is, nothing could be better,
that's in some ways more important, so super!
Hopefully you can start to see
that relationship as my PD gets wider,
because PDs are almost always more narrow
than the frame PD is,
the less you need to decenter the lens.
The less problems you're gonna have,
the less chance you won't have cutout,
the less thickness you're going to have,
all kinds of issues, so hopefully you see that relationship.
I have a frame PD of 69 millimeters,
because I have an A of 52 and a DBL of 17.
Seven plus two is nine, five and one is six.
My boxing system somewhere on that frame
would be marked like that
and I'd have minus one seventy five,
the 75 not enough power there to worry about,
you could just use your boxing system.
As powers increase, as things become more complex,
yes, you would want to use a PD stick
and verify or confirm that those
are accurate measurements.
I have a human PD of 64 pupil to pupil.
Frame PD out here, human here.
If I have a frame PD of 69,
and I take away 64 I have a difference of five.
Five divided by two, I end up with
two point five millimeters in decentration per eye.
And because the frame is a little bit
smaller than the last one
and my PD is a little bit wider,
I need to move that lens a little tiny bit
just two and a half millimeters.
Just two and a half millimeters
to get that OC to line up with that wearer's pupil.
Do that and you're gonna have a great pair of glasses.
Let's see what that would look like in the blocker.
For example three I have just a little tiny
two and a half millimeters of movement.
That would be my zero.
That would be one, that would be two,
that would be two and a half.
Again right moves right for indecentration,
left moves left.
May as well go ahead and load that block.
That would be on center or zero.
Moving that OC over two and a half millimeters.
Sticking my block on.
Checking it, let me see if I can
do this in a different way.
Again, this is kind of more of a check your work
kind of thing but if you take a look at this lens,
right lens, looking through it as if
you were wearing a new pair of glasses, like so,
the center of the block, that little tiny dot there,
that would be the center of the eyewire opening.
And if I look, I can see that my OC,
my black dot or X right there has been displaced
two and a half millimeters to the left or in decentration.
Anyway, it's just kind of a check your work step.
Notch, notch, notch.
Zero, one, two and a half.
Left lens.
One, two and a half.
Beautiful.
Double check left lens, center of my block
would be the center of my eyewire opening,
the little X would be to the right of that,
that would be left when I looked in as it was worn.
That's what it would look like in the blocker.
Thank you so much for watching.
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