Miscellaneous Flashcards

0
Q

One meter has the power of how many diopters?

A

1

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1
Q

Formula to find power of a lens:

A

F+B=P

(Front of lens + Back of lens = Power of Lens(

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2
Q

1” = _____mm

A

25.4

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3
Q

Formula to find Focal Length:

A

F= 1/D

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4
Q

Characteristics of Minus Lenses

A
  • minify image
  • thinner middle
  • with motion
  • are for myopia only
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5
Q

Minus lens shapes

A
  1. Bi-concave
  2. Piano-concave
  3. Meniscus
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6
Q

Plus Lens Shapes

A
  1. Bi-convex
  2. Plano-convex
  3. Meniscus
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7
Q

Characteristics of Plus Lenses

A
  • magnifies
  • thick center
  • against motion
  • corrects: hyperopia, presbyopia & aphakia
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8
Q

Light rays become parallel at how many feet?

A

20 (to infinity unless interrupted)

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9
Q

Three Bands of Ultra Violet Light:

A

A B C

A & B: use UV protection
C: is absorbed by atmosphere

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10
Q

The separation of Light Rays into Colors is called:

A

Dispersion

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11
Q

Reverse Slab is made in only:

A

CR-39 & ST28

It is pre-made on the front of the most plus lens

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12
Q

Purpose of slab off

A

To balance the prism on bi-focals that have a imbalance due to rx,
Add slab off to grind a new oc on the back of the most minus or least plus lens.

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13
Q

Index of Refraction and ABBÉ value of:

CR-39

A

1.49

59-60

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14
Q

Index of Refraction and ABBÉ value of:

Crown Glass

A

1.523

60

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15
Q

Index of Refraction and ABBÉ value of:

Flint Glass

A

1.70

30-55

16
Q

Index of Refraction and ABBÉ value of:

Hi-index

A

1.60

43

17
Q

Index of Refraction and ABBÉ value of:

Polycarbonate

A

1.58

29-31

18
Q

Characteristics of CR-39

A

Plastic
“Columbia Resin 39” was the 39th batch.
Tints great.

19
Q

Characteristics of crown glass

A

Twice as heavy as plastic. Great optics. Very durable. Uv coating is ugly yellow. Tints are made in the glass

20
Q

Flint glass

A

Had flint & lead oxide to refract more. 1.70. heavy. Not used any more

21
Q

To find the frame pd:

A

Eye size + dbl

22
Q

To find blank size:

A

Frame PD (eye size + dbl) - patient PD = total decentration. Add ED + total decentration

23
Q

Details of the drop ball test

A

5/8 inch ball
6/10ths of an ounce
Dropped 50 inches

24
Q

Splay of nose pads

A

Flat side of nose

25
Q

Frontal nose pads

A

Pressure on top or bottom of nose pad

26
Q

Vertical nose pad

A

Pad too close to eye

27
Q

Dress eyewear

A

Z80.1

28
Q

Industrial eyewear

A

Z87.1

29
Q

Base curves of lenses

A
Plano  -600-----  up
\+200  -400----- -600
\+400  -200----- -400
\+600  +200 ---- -200
\+800  +200 ----- +500
\+1000 +500 ---- +800
\+1200  +800-----+
30
Q

What are light waves measured in?

A

Nanometers

31
Q

What is the longest and shortest waves?

A

Red is longest and violet is shortest.

32
Q

Uv is just beyond what spectrum

A

Red