WEBVTT

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In this video, I wanted to show you how
to use the lensometer.

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The lensometer is a device used
for checking prescription glasses

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and can be a little confusing.

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The first step is to put the glasses
and the frames here,

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and you can see this platform moves
up and down.

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And you want to put
the optical center of this lens

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such that it aligns here,

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and this little brace
holds the glasses in place.

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You want to make sure both glasses

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are touching the bottom
of this platform.

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Turn it on, and then look
through this eye piece,

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and this is what you should see.

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Now, the hard part
with using this machine

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is you have to use two dials
at the same time.

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There's an axis dial up here

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and there is a focus dial
down here.

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And you spin both of these,

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and the goal
is to get the three small lines--

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the three little lines next
to each other,

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lined up and in focus.

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So if we zoom in,
we can see that there's three lines.

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You want to get them lined up
and in focus.

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And then you can mark
down what this is.

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If you look on our dial here
and our focus,

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we can see this is a 3.25,
so that's the sphere.

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The sphere is 3.25.

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Now you move the focus
in whatever direction it takes

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in order to get the three fat lines
in focus.

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And the difference
between those is your cylinder power.

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So we went up +2.75 to get to 6.0.

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So that's our cylinder, +2.75.

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Our axis looks like it's
about 12 degrees.

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So here is our prescription.

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Now, to get the bifocal power,

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I need to move the glasses up
to the bifocal segment

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and see how much
you need to change it

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to get the three fat lines
in focus again.

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So we went from +6.0 to +8.5,

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so our add is +2.50.