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Ophthalmic optics 2 > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

What is the visible spectrum?

A

380-760 nm

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2
Q

What is the UV spectrum

A

200-380 nm

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3
Q

Describe ophthalmic crown glass transmission characteristics

A

10% reflection, not a good UV blocker

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4
Q

Describe CR-39 transmission characteristics

A

10% reflection, improved UV blocker

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5
Q

Describe polycarbonate transmission characteristics

A

10% reflection, great UV blocker

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6
Q

What is the reflection equation?

A

Note that it’s like n2-n1

front surface: (1.5-1)

back surface (1-1.5)

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7
Q

n for crown glass

A

1.523

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8
Q

n for Cr-39

A

1.499

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9
Q

n for polycarbonate

A

1.586

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10
Q

n for trivex

A

1.53

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11
Q

n for

Crown glass

CR-39

Polycarbonate

Trivex

A

Crown glass N=1.523

CR-39 N= 1.499

Polycarbonate N=1.586

Trivex N=1.53

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12
Q

What is essential for calculating Lambert’s law of absorption?

A

the trasmittance factor (q)

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13
Q

What is ultimate transmission?

A

multiplying the seperate transmition of each lens to find ultimate transmission

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14
Q

Opacity equation:

A

O= 1/Transmission

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15
Q

Ultimate opacity equation:

A

O*O*O or (1/T)(1/T)

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16
Q

What is the Abbey for crown glass?

A

59

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17
Q

What is the Abbey for CR-39?

A

58

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18
Q

What is the Abbey for polycarbonate?

A

30

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19
Q

What is the Abbey for Trivex?

A

43-46

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20
Q

What are the abbey numbers?

A

Crown glass Abbey 59

CR-39 Abbey 58

Polycarbonate Abbey 30

Trivex Abbey 43-46

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21
Q

What are the specific gravities?

A

Crown glass specific gravity 2.54

CR-39 SG 1.32

Polycarbonate SG 1.20

Trivex SG 1.11

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22
Q

Crown glass specific gravity

A

2.54

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23
Q

CR-39 specific gravity:

A

1.32

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24
Q

Polycarbonate specific gravity:

A

1.20

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25
Q

Trivex specific gravity

A

1.11

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26
Q

Optical density equation:

A

OD = -log(Transmission)

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27
Q

Distracting glare is…

A

caused by annoying lens reflections. AR can help

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28
Q

Discomfort glare is….

A

in field of view but does not interfere with resolution

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29
Q

Disability glare is….

A

causes lower contrast, does interfere with resolution. Central 10 degrees of visual field. Prevent with deeper tints or photochromics

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30
Q

Reflected glare is…

A

caused by reflected light. AKA blinding glare

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31
Q

polarized lenses removes…. How is the transmission axis ortiented?

A

specularly reflected horizontally polarized light. the transmissiona axis is at 90 degrees

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32
Q

Brewster’s angle equation

A

Tan i = n.

i is the angle between ray and the normal

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33
Q

What is Malus’ law of polarization?

A

I0 = Icos2 θ​

I = initial light intensity

I0 = new light intensity

theta = angle between transmission axis of the 2 polarizers

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34
Q

What is “In-mass” photochromics?

A

spiropyran photochromics throughout the lens

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35
Q

What is imbibed photocrhomic technology?

A

spiropyrans are in a surface coating for consistant darkening

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36
Q

What are the steps to get frames into standard alignment?

A
  1. Horizontal alignment,

2 Vertical alignmnet (4 point touch test)

3: Open Temple Alignment (90-95 deg)
4: Temple Parallelism (flat surface touch test upsidedown)
5: Alignment of the bent-down portion of the temple (rightside up)
6: Temple-fold angle

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37
Q

What is invovled in Vertical alighment of frames (step 2)

A

4 point touch test (lenses and nose are all in same plane), make sure there is no X-ing

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38
Q

___% of lenses are AR coated in the US

A

30

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39
Q

Neutralization in AR happens when the path difference is an ___ number of half wavelengths

A

odd

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40
Q

Reinformcement in AR happens when the path difference is an ___ number of half wavelengths

A

even

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41
Q

The ___ the index of refraction, the greater the glare and reflections

A

The higher the index of refraction, the greater the glare and reflections

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42
Q

Index of coating equation:

A

nc= sqrt (nL)

nc = index of coating needed

nL = index of lens

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43
Q

The best AR should have a thickness ___% of the desired wavelength

A

The best AR should have a thickness 25% of the desired wavelength

44
Q

What wavelength is generally selected for AR?

A

want to block 555 nm

45
Q

How is AR applied to glass?

A

cleaning, heated in vaccum, AR heated even higher

46
Q

How is AR applied to plastic?

A

clean, bake to remove water, 100 deg C heating in vaccum, quartz for outer layer.

47
Q

how long does AR take to apply?

A

4 to 10 hours

48
Q

What is the outermost layer of AR?

A

hydrophobic coating that also increases hardness to prevent scratching

49
Q

Most AR coatings are ___ layers

A

Most AR coatings are 5-6 or as many as 11 layers

50
Q

How are mirrored coatings accomplished?

A

constructive interference on front of lens

51
Q

what are the two types of mirror coatings?

A

metalic (scratches easily) and

dielectric (durable)

52
Q

What is a mounting? What are the 3 brands?

A

The “frame” for rimless or semirimless glasses

Balgrip/Ilford

Numont

Wils-Edge

53
Q

Keyhole

A

A bridge type (the nose is the “key”)

54
Q

Saddle

A

bridge type that is curvy on top and bottom, does not protrude

55
Q

comfort bridge

A

has ugly nose piece

56
Q

Semisaddle

A

Bridge protrudes a little in front and has plastic nose pads

57
Q

What is a modified saddle?

A

the semisaddle (has plastic nose piece).

58
Q

What is the W bridge?

A

it’s the metal saddle (has no nose pieces)

59
Q

What are the different endpiece types? 6

A

American, English, French, butt-type, mitre-type, turn-back

60
Q

Which hinge type has the “shield” visible from the font?

A

Riveted hinge

61
Q

Which hinge has apperatus anchored directly into plastic?

A

Hidden hinge

62
Q

What are the different temple styles?

A

skull

library

convertible (either of 1st two depending on how bent)

riding bow (curve in plastic)

comfort cable (curve in metal)

63
Q

Which temple is curved in plastic?

A

riding bow

64
Q

Which temple is curved in metal?

A

comfort cable

65
Q

What are some problems you can have by correcting refractive error of anisometropia?

A

Magnification differences, vertical imbalance when reading, and horizontal vergence problems

66
Q

Anisometropia is….

A

when the Seq of both eyes differ by 1.00 D or more

67
Q

Anisometropia vs aniseikonia?

A

Anisometropia : unequal refractive error

aniseikonia: differing retinal image sizes

68
Q

If a patient’s reading position is 10 mm below optical centers, how much anisometropia can they have before they will have symptomatic vertical imballance?

A

1.00D of aniso. This means that the person experiences 1 prism D of vertical imballance.

69
Q

If there is too much vertical imbalance for reading because of anisometropia, what lens technique can fix the vertical imballance?

A

Slab off removes base down from the most minus lens

70
Q

What is aniseikonia?

A

unequal image retinal size or unequal shape differences between retinal images

71
Q

symmetrical vs asymmetrical aniseikonia:

A

Symmetrical: size change is equal in all directions

Asymmetrical: meridonial image size is changed in one dimention (not both)
or there is disortion (progressive changes in dimmensions)

72
Q

What is asthenopia?

A

eyestrain from dissimilar images. eyes feel “funny”, HA, photophobia, nerviousness.

occluding an eye relieves these symptoms

73
Q

1.10 would be ___% magnification, 0.92 would be ___% minification

A

10% and 8%

74
Q

What is the total spectical magnification equation?

A

Shape factor * power factor

( 1 / (1-[t/n]F1) ) * (1 / (1-hFv)

75
Q

What is the shape factor equation?

A

1 / (1- [t/n] F1)

76
Q

What is the power factor equation?

A

( 1 / (1-hFv)

77
Q

What is the equation for changing spec RX into CL RX?

A

Fs / (1 - dFs)

78
Q

How does astigmatism affect spec mag? What about in CLs?

A

each diopter of cyl makes a difference in mag by 1.5% 0.3% for CLs

79
Q

uncorrected axial myope or hyperope has larger image size?

A

myope has larger image size

80
Q

uncorrected refractive myope or hyperope has larger image size?

A

neither! it’s about the same

81
Q

What is Knapp’s Law?

A

axial ametropic eyes corrected with specs will have similar retinal sizes as an emetropic eye.

82
Q

According to Knapp’s law, how are axial myopes best treated? Refractive myopes? what does correcting in these ways help avoid?

A

axial best treated with spectacles (but CLs are ok too, clinically)

refractive with CLs

these help avoid Aniseikonia

83
Q

A high Rx greater than ___D is usually from abnormal axial legnth

A

+/- 4.00 D

84
Q

low refractive error (probably less than +/-4.00D) is refractive or axial?

A

low refractive error is a combination of both refractive and axial!

85
Q

Image size differences greater than ____% will usually result in loss of binocularity

A

Image size differences greater than 5% will usually result in loss of binocularity

86
Q

What is the “rule of thumb” for aniseikonia?

A

1.00D difference between eyes has 1% image size difference

87
Q

What is the most popular plastic frames material?

A

Zyl, or cellulose acetate

88
Q

Zyl characterisics: hypoallergenic, lightweight, strong, flexible…

A

hypoallergenic yes

lightweight yes

strong no

flexible no

89
Q

What are Zyl advantages/disadvantages?

A

colors, easily worked, can grow/shrink for sizing errors

Brittle with age, lose luster, heavier than other plastic frames

90
Q

Propianate characteristics:

A

hypoallergenic yes very hypoallergenic

lightweight yes very hypoallergenic

strong no

flexible yes

91
Q

What are some advantage/disadvantages of Propionate?

A

less “dulling” food flex, very lightweight and hypoallergenic

not as common a zyl, heat and solvent sensitive. lens size has to be exact

92
Q

Optyl characteristics

A

Thermoelastic

hypoallergenic yes

lightweight yes

strong yes

flexible yes

93
Q

Optyl advantages/disadvantages

A

very light, excellent shape retetion, hypo-allergenic, very heat and solvent resistant

Difficult adjustments that require heat, will not shrink

94
Q

Aluminum characteristics

A

hypoallergenic no

lightweight yes

strong yes

flexible no

corrosion resistant yes

95
Q

Aluminum advantages/disadvantages

A

good to very good resistance, high luster, light

lens often have “gapping”, complicated manufacturing with rivets

96
Q

Monel characteristics

A

most widely used, has nickel (and copper, etc)

hypoallergenic no

lightweight no

strong no

flexible highly flexible

corrosion resistant yes (when plated)

97
Q

Monel advanteges

A

Cost-effective and efficient, malleable

medium corrosion resistance unless plated, heavier

98
Q

Titanium characteristics

A

hypoallergenic yes

lightweight yes

strong yes

flexible no

corrosion resistant yes

99
Q

Titanium pros/cons

A

very light and hard, hypoallergenic

very expensive, not very flexible

100
Q

Flexon characteristics, pros/cons

A

Titanium alloy (Marchon), AKA memory metal

hypoallergenic yes
lightweight yes
strong yes
flexible highly flexible can bend to original shape
corrosion resistant yes

hard to adjust, patterns not as available

101
Q

Beryllium, characteristics, pros/cons

A

low-cost alternative to titanium

hypoallergenic no
lightweight yes
strong yes
flexible yes, but springy
corrosion resistant yes

good for salty/acidic patients

102
Q

Stainless steel characteristics, pros/cons

A

steel chromium alloy

hypoallergenic yes
lightweight yes
strong yes
flexible no, springy
corrosion-resistant yes

103
Q

Which nosepad is hard and nonflexible?

104
Q

Which nosepad is flexible, slippery?

105
Q

Which nosepad is grippy and sticky?

Ophthalmic optics 2 (4 decks)

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