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Volume 2 Course# OCPP 102 > Lens material and design > Flashcards

Lens material and design Flashcards

1
Q

Crown glass
Index of refraction:
Specific gravity (density):
Abbe Value:

A

1.523
2.54
59

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2
Q

CR-39
Index of refraction:
Specific gravity (density):
Abbe Value:

A

1.498(1.50)
1.32
58

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3
Q

Polycarbonate
Index of refraction:
Specific gravity (density):
Abbe Value:

A

1.586
1.22
29-32

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4
Q

TRIVEX
Index of refraction:
Specific gravity (density):
Abbe Value:

A

1.53
1.11
43-46

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5
Q

NXT
Index of refraction:
Specific gravity (density):
Abbe Value:

A

1.53
1.11
43-46

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6
Q

Hard Resin 1.67
Index of refraction:
Specific gravity (density):
Abbe Value:

A

1.67
1.35
32

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7
Q

Which is a better product, a lens with a low Abbe value or a high Abbe value?

A

High Abbe value

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8
Q

What is the name of the instrument used to check to see if a glass lens has been heat treated?

A

Colmascope and Polariscope

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9
Q

Crown glass lenses have UV protection inherent in the material and do not need additional UV coatings.

True or false

A

False

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10
Q

Arrange these lens materials in order starting with the one that has the most UV protection and ending with the one that has the least protection. 1 being the most and 4 being the least.

Crown glass
CR-39 with transitions
Polycarbonate
Clear CR-39

A

1 polycarbonate
2 CR-39 with transitions
3 Clear CR-39
4 Crown glass

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11
Q

Listing a lens material as part of the eyeglass prescription is inappropriate.

True or false

A

False

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12
Q

What do you look for when you are trying to determine which lens material would be the thinnest?

A

Highest index of refraction

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13
Q

Which lens characteristic will tell you how much chromatic aberration a lens will have?

A

Abbe value

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14
Q

What is chromatic aberration?

A

Color distortion due to the material when light passes through it, dispersion of light.

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15
Q

Polycarbonate is the softest spectacle lens material.

True or false

A

True

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16
Q

How are glass lenses hardened? Briefly describe the methods.

A

Heat treating is done in two to three minutes in a small furnace and chemical treating is done by immersing lenses in molten salt.

17
Q

How long does the FDA require that you keep a patients file?

A

3 years

18
Q

What does product liability mean for opticians? Be specific for eyewear types.

A

The product was not up to accepted standards.
Dress eyewear: Drop ball test
Safety eyewear: Z87 meets and thickness standards
Sports eyewear: Faulty design, impact resistance, ASTM 803 met when needed.

19
Q

Since the fabricating laboratory takes full responsibility for the accuracy of safety and sports eyewear, verification of lens thickness by the dispenser is unnecessary.

True or false

A

False

20
Q

The Federal Trade Commission established Eyeglasses 1 in 1978 and Eyeglass 2 in 1989. What’s the difference between them?

A

Eyeglass 1 is the prescription release rule and lists minimum information to be included in the Rx. Eyeglass 2 no longer lists minimum information needed to make spectacle Rxs.

21
Q

What does the FDA regulate for opticianry (excluding contact lenses) and when did they start doing it?

A

Impact resistance in 1971

22
Q

Both scratch-resistance and anti-reflective coatings are harder than the plastic lens material they are adhered to.

True or false

A

True

23
Q

The harder the material the more impact resistant it will be.

True or false

A

False

24
Q

Which glass lenses is exempt from the drop ball test?

A

Slab-off lenses
Cataract lenses
Custom laminate lenses

25
Q

If four lenses were made with the exact same curves and thickness, which lens would be the heaviest?

A

Crown glass

26
Q

A lens for safety glasses must be 3.0mm thick if it is CR-39 or glass, but if it is polycarbonate the thickness must be at least 2.0mm.

True or false

A

False

Volume 2 Course# OCPP 102 (8 decks)

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