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ABO Prep > Characteristics Of Ophthalmic Lenses > Flashcards

Characteristics Of Ophthalmic Lenses Flashcards

1
Q

Name the advantages of Glass Lenses

A
  1. Superior optics
  2. Super Scratch Resistant
  3. Chemically Resistant
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2
Q

Name the Disadvantages of Glass Lenses

A
  1. Doesn’t filter UVA or UVB
  2. Not impact resistant
  3. Thick and extremely heavy
  4. Possible to shatter
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3
Q

How are glass lenses created?

A

By heating and melting materials to a crude finish which has to be roughed down and polished to an acceptable finish

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4
Q

How are Fixed Tints added to Glass lenses?

A

By mixing special crystals with the “clear” crystal in the process that is then baked in specially designed ovens that results in not only the color but a permanent filter in the lens

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5
Q

Is there any filter with Artificial tints on Glass Lenses?

A

None

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6
Q

What are the standard Indices of Glass Lenses?

A

Standard 1.62, 1.70, and 1.80

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7
Q

What does CR39 stand for?

A

Columbia Resin which took 39 tries to invent it

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8
Q

What are the advantages of CR39 lenses?

A
  1. Half the weight of Glass
  2. Can withstand high temperatures
  3. Less expensive
  4. Accepts Tints easily
  5. 5-10x stronger then glass
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9
Q

What are the disadvantages of CR39?

A
  1. Not UVA/UVB filtered
  2. Not impact resistant
  3. Thickest of all plastic, non-glass, lenses
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10
Q

What are the advantages of Polycarbonate lenses?

A
  1. Thin and Lightweight
  2. Impact resistant
  3. UV protection
  4. 5-20x stronger than plastic
  5. Abrasion resistant coated
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11
Q

What are the disadvantages of Polycarbonate Lenses?

A
  1. Small number of people indicate their vision seems distorted through poly lenses
  2. Not very thin for high prescriptions
  3. Hard to tint
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12
Q

Which lens material is used for Blackhawk helicopters?

A

Trivex lenses

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13
Q

What are the advantages Trivex lenses?

A
  1. High tensile strength
  2. Chemical resistance
  3. Lightweight
  4. Impact and abrasion Resistant
  5. UV protection
  6. 5-20x stronger than plastic
  7. Crisp clear optics
  8. Great for drill mounts
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14
Q

What are the disadvantages of Trivex lenses?

A

Thicker than poly, but thinner than CR39

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15
Q

What is the Index of Trivex lenses?

A

1.53

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16
Q

What is the Index of Polycarbonate?

A

1.59

17
Q

What are the standard indices of High Index lenses?

A

1.60, 1.67, 1.70, 1.74

18
Q

What are the Advantages of High Index Lenses?

A
  1. Lighter lenses bc they’re made of less material.
  2. UV Protection
  3. Good for strong Rx’s
  4. Suitable for semi-rimless frames
  5. Better cosmetic appeal
  6. Eyes typically appear less magnified/minimized in plus/minus lenses
19
Q

What are the Disadvantages of High Index lenses?

A
  1. Higher cost for the practice and the patient
  2. Not as lightweight or impact resistant as poly or trivex
  3. Higher Index of refraction which makes ABBE value worse
  4. 1.70/1.74 not suitable for drill mount frames
  5. reflects more light
20
Q

What is another name for ABBE value?

A

V - value

21
Q

What does ABBE Value measure?

A

a lens materials dispersion of light

22
Q

When the ABBE Value of a lens is low, what does that mean for the separation of color?

A

the separation of color is greater

23
Q

The greater the separation of color, what effect does it have on the image the eye sees?

A

image becomes distorted due to the inability of the lens to focus all colors onto the same focal point

24
Q

Does Trivex have more or less unwanted abberation then Poly, and how much?

A

trivex has less, 35% less

25
Q

What is the ABBE value of the human eye?

A

45

26
Q

What is the ABBE value of Glass?

A

59

27
Q

What is the ABBE value of CR39?

A

58

28
Q

What is the ABBE value of Trivex?

A

45

29
Q

What is the ABBE value of 1.60?

A

36

30
Q

What is the ABBE value of 1.67?

A

32

31
Q

What is the ABBE value of Poly?

A

30

32
Q

What is the ABBE value of 1.74

A

32

33
Q

What is Chromatism?

A

a lenses level of color separation(it’s ABBE value)

34
Q

Which lens has the highest level of Chromatism, or lowest ABBE value?

A

Poly

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