(grunting)
(upbeat music)
- Hello and as always I would like to welcome you
to the Laramy-K OpticianWorks training center.
Where this week we are going to
just head right over at the whiteboard
and pick up right where we left off last week.
Last week using Vogel's Rule we have determined D1
or what the front base curve would be
for the prescriptions given.
We ended up with a +3.00, a +5.00 and a +7.00.
Now since we have D1
and we have DL we can solve for D2
or the back curve or curves we're gonna put
on this lens to create this power.
Let's take a look at our -5.00 -2.00
a little bit closer one more time.
If we're looking at that,
if I have my front base curve.
If I clocked that in the perfect world
as a concept or an idea I'd end up with +3.00.
If I flip that lens over
and I look at my shallower green curve,
I need to determine what I what would need to put there
if have a +3.00 on the front to end up with a -5.00.
90 degrees away my red band, the steepest curve,
the strongest curve the one with the shortest radius,
the thickest edge, is going to be my -7.00.
So let's figure out how we would determine that.
You may very well just look at this and see it.
That's great, super.
I'd how to obviously go -3.00 to get zero
and then an additional five diopters to reach my -5.00.
So I'd have a -8.00, great.
If you can just see that that's wonderful.
If that doesn't quite work for you
we can think of it as
we know that a -5.00 combined with an unknown
is gonna end up at a +3.00.
So if I take my -5.00
and I do the opposite, I take my -5.00
and I subtract three I end up at -8.00.
So whether you can see it
or you need to do a little bit of math.
Our toric curve, the curve that will create
the shallower curve give us our -5.00
our weakest power on the lens,
our spherical portion is gonna be a -8.00.
For this prescription if I have -1.75
and I take away my five I end up with
a -6.75 for my toric curve.
The one that will create this portion of my lens power.
On my plus it works just a little bit different.
I can simply take my +1.50 subtract seven,
I end up at a -5.50.
We're not done those curves are only gonna give us
our spherical portion.
Now we need to come in
and grind that steeper curve
90 degrees apart on the back of it
and determine what that power is gonna be.
How do we do that?
We look at our cylinder value.
That is where our cylinder comes from.
Our cross curve to create our -7.00 power
is gonna two diopter steeper than our -8.00.
I am gonna have a -10.00.
Two diopters difference.
To create a -2.75 I'm gonna need an additional
full diopter stronger.
I'm gonna have a -7.75.
One difference between the two.
Hate using that word,
I almost said as simple as that.
Nothing is simple in this stuff
but you can see where this comes from.
My +0.25 and my other power
and my -5.50 combined with my -1.25
I'm gonna have a -6.75.
And again that looks and acts a little bit different
because this is a plus prescription
as opposed to a minus.
So there we have solving for D2 when we have DL and D1.
You may need to run through this a few times.
You may just see it.
You may need to think about it a little bit more.
Go back to looking at the actual lens itself
and thinking about it.
Next week we're gonna talk a whole lot more
about the actual creation of these curves.
I'm gonna show you that in action
and we're gonna talk a little bit
about where thickness comes from.
So until then watch it again
see if you get it
and I will see you next week.
Thanks for watching.
If you are watching this on YouTube
please hit the subscribe button.
If you're watching this on Facebook,
please share it with some other folks.
Thanks.