Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Opthalmic Optics > Handout 2 > Flashcards

Handout 2 Flashcards

1
Q

Chromatic dispersion, aberration, and disperse power all affect

A

ABBE value

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Travel more SLOWLY through material (undergo the greatest refraction)

A

Shorter wavelengths (violet and blue)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Who has the highest index of refraction between blue and red

A

Blue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Who has the higher index of refraction short or long wavelengths

A

Shorter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Travel faster (undergo the least refraction)

A

Longer wavelengths

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

(Fraunhofer D/yellow) Relationship between D and n of a lens/prism?

A

D of a lens/prism is based on the n that the material has for this chosen standard reference wavelength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Index of refraction equation

A

n= velocity of light in air or vacuum / velocity of light in material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Different colors have different ___ in the same material

A

Index of refractions (n)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Based on Fraunhofer D/ yellow He line wavelength is

A

587.56 nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Different wavelengths of light have different n for the same material. This is called:

A

Chromatic dispersion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Chromatic aberration

A

Because of the chromatic dispersion of the lens the lens fails to focus all colors to the same convergence point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

The mean dispersion of a material is

A

The difference in the refractive indices of red light (656nm) and blue light (486nm) for that material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Fraunhofer C line

A

Red

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Fraunhofer F line

A

Blue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Dispersive power

A

Dispersion of a material is more commonly related to the refractive index of 587.6 nm (nD) (yellow) by the number known as the dispersive power

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

The dispersive power equation will tell us

A

How great is the color spread by this material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Low dispersive power

A

Little to no chromatic aberrations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

High dispersive power

A

More chromatic aberration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

The reciprocal of dispersive power

A

Abbe value

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Low dispersive power will have ___ chromatic aberrations

A

Little to none

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

ABBE value desired for best optics

A

High abbe value

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is specific gravity

A

Ratio of the weight of a substance to the weight of water with the same volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Other names for Abbe value

A

Nu value, v, or constringence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Abbe value for poly

A

30, low abbe value

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Reflectance

A

The amount of light reflected at each surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Reflectance produces

A

Produce ghost images, falsification of image position, haze, decreased contrast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Reflectance effect on cosmesis

A

They obscure the wearers eyes with glare and draw attention to glasses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Reflectance equation is

A

IR equation on equation sheet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Lens is reflected from what portion of the lens

A

Front and back

Aka lens refractive index

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

A typical, non coated, ophthalmic lens reflects

A

8% or more of incident light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Transmittance (t) is

A

The fraction of incident light passing through lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Transmittance varies for

A

Wavelengths, especially for tinted lenses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Major forms of absorptive lenses

A

Tinted, glass coating, photochromic and polarizing lenses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Absorptive lenses act as filters by

A

Reducing the amount of transmitted light (tinted or colored glasses)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Color lenses absorb

A

Different wavelength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Increase in index of refraction = ___ light reflected and ____ light transmitted.

A

High reflectance

Low light transmitted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

(2) have hard coatings that incorporate special UV absorbers

A

Poly and high index

38
Q

(2) do not provide adequate protection and require UVtreatment

A

Glass and CR39

39
Q

Lenses without UV protection can cause harm because

A

They cause pupils to dilate, allowing more harmful UV radiation to enter eye

40
Q

Uv radiation transmitted to ocular surfaces

A

200-380nm

  • invisible to human eye
  • contains more energy than visible light
41
Q

Lens that meets impact safety requirements described by z87.1 means

A
  • it’s at least 2.00mm

- it passes the high velocity impact test (1/4” steel ball, traveling at 150ft/s)

42
Q

The drop ball test is ___. What determines if pass or fail?

A

FDA regulation for impact resistance. Pass= lens must not fracture

43
Q

What exactly is a fracture in a drop pall test

A

Lens cracks into 2 or more pieces or lens material detaches from surface

44
Q

Drop ball test was designed for

A

Glass, plastic lenses can be batch tested

45
Q

Lens material that is not inherently impact resistant and therefore must be treated “tempered” to pass FDA test

A

Glass, they are individually tested

46
Q

What does tempering mean

A

Place the outer surface of the lens in a state of compression. Used for glass lenses. Either thermal or chemical

47
Q

Thermal tempering

A

Lens is heated to ~650 degrees then rapidly cooled-> places outer surfaces in a state of compression and the inner portion in a state of tension-> causes the glass to crumble into small grain chucks when broken instead of sharp pieces

48
Q

What is chemical tempering

A

Heated salt bath (~400 C) larger ions from slat exchanges w small on lens surface-> surface is compressed, inner portion is in tension. = small granular chunks instead of sharp pieces

49
Q

Polycarbonate is __ more impact resistant than CR39

A

21x

50
Q

Effects of AR coating/ or scratch resistance on the lense’s impact resistance

A

decreases Impact resistance

51
Q

Surface starching and pitting i lenses reduces

A

Impact resistance

52
Q

(2) are intrinsically impact resistant (different amounts tho)

A

CR39 and poly

53
Q

Glass lenses advantages

A

Optical clarity, resists scratching, not easily affected by environmental factors

54
Q

Glass disadvantages

A

Weight and not impact resistant

55
Q

Semi finished lens

A

Back surface remains unfinished

56
Q

Finished lens

A

Back surface is ground and polished

57
Q

Ophthalmic crown glass, flint glass, barium crown glass

A

Types of glass lenses

58
Q

Ophthalmic crow glass is used for

A

Distance portion of glass bifocal and trifocals lenses

59
Q

Flint glass index of refraction

A

1.580-1.690 (higher than crown)

60
Q

Flint glass used for

A

Fuse bifocal segments (higher n than distance lens)

61
Q

Flint glass was historically used for __ until replaced

A

High powered lenses

62
Q

Barium crown glass used for __ its high index is __?

A

Fused bifocal segments (higher index than distance)

1.541-1.616 (higher than crown)

63
Q

“Organic material”

A

Plastic

64
Q

Hard resin lenses that are made by “casting” where they begin as liquid and cured in oven where cross linking occurs and cant be melted back down to the liquid monomer resin

A

Thermosetting / CR39

65
Q

Most common type of plastic lens

A

CR39

66
Q

CR39 block __ of incident UV

A

55%

67
Q

Can be melted and cooled back and forth from liquid to solid states “injection- molding”

A

Thermoplastic/ poly

68
Q

Material recommended for monocular, kid and safety/sports wear

A

Polycarbonate

69
Q

Lens that block 98% of incident UV light

A

Poly

70
Q

Whats a disadvantage of poly

A

“Soft” required antiscratch coating, unable to tint

71
Q

Why is trivex so names

A

Because of its 3 desired qualities, good ABBE, excellent impact resistance, and extremely light weight

72
Q

Lens that would reflect most light if untreated

A

Flint

73
Q

Combines both thermosetting and thermoplastic monomers giving it superior tensile strength

A

Trivex

74
Q

Material of choice for drill mountings

A

Trivex

75
Q

Is trivex able to be tinted

A

Yes

76
Q

Advantages of high index lenses

A
  • Bend light more efficiently and therefore lenses can be thinner and light
  • thinned is limited by impact resistance standards and lens stability
  • can use glass or plastic
77
Q

High index lens from glass material

A

Flint (1.6)

Barium (1.541)

78
Q

High index plastics

A

Polycarbonate (1.59)

Trivex (1.53)

79
Q

Disadvantages of high index

A

Lower ABBE

Increased reflections

80
Q

Power of the front surface of a spectacle lens. May be used to refer to flatter meridian of a toric surface

A

Base curve

81
Q

FDA regulation that is the law and must be followed

A

CFR801.410

Impact resistance

82
Q

Z80.1

A

Recommendations for prescription ophthalmic lenses

83
Q

Z80.3

A

Non prescription sunglasses and fashion eyewear requirements

84
Q

Z80.5

A

Dress ophthalmic frames

85
Q

Z87.1

A

Occupational and educational eye and face protection

-federal requirement

86
Q

Z80.1 and z80.3

A

FDA mandates the impact resistance of lenses

87
Q

ANSI standard thats a federal requirement

A

Z87.1

88
Q

Z87.1 has 2 levels of safety requirements

A

Non impact and impact

89
Q

Non impact requirement of z87.1

A
  • 3.00mm minimum thickness except more mm can have 2.5 edge thickness
  • drop ball test
  • manufactures logo on lens
  • should tell patient that it meets basic impact requirement but should not be relied up for high impact exposure
90
Q

impact requirement of z87.1

A
  1. 00 mm thickness
    - high velocity impact test
    - manufactures logo with a + on the lens

Opthalmic Optics (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions