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Ophthalmic optics 2 > Exam 1 pruned for exam 2 > Flashcards

Exam 1 pruned for exam 2 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-n1front 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 forCrown glassCR-39PolycarbonateTrivex

A

Crown glass N=1.523CR-39 N=1.499Polycarbonate N=1.586Trivex 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

OOO 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 59CR-39 Abbey 58Polycarbonate Abbey 30Trivex Abbey 43-46

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21
Q

What are the specific gravities?

A

Crown glass specific gravity 2.54CR-39 SG 1.32Polycarbonate SG 1.20Trivex 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

causeslower 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= Icos2θ​I = initial light intensityI0 = new light intensitytheta = angle between transmission axis of the 2 polarizers

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34
Q

What is “In-mass” photochromics?

A

spiropyranphotochromics 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

Reinformcementin 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 needednL = 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) anddielectric (durable)

52
Q

What is a mounting? What are the 3 brands?

A

The “frame” for rimless or semirimless glassesBalgrip/IlfordNumontWils-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

skulllibraryconvertible (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 erroraniseikonia: 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 sizeor unequal shape differences between retinal images

71
Q

symmetrical vs asymmetrical aniseikonia:

A

Symmetrical: size change is equal in all directionsAsymmetrical: meridonialimage 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 refractivemyope 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 specswill 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 CLsthese 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 yeslightweight yesstrong noflexible no

89
Q

What are Zyl advantages/disadvantages?

A

colors, easily worked, can grow/shrink for sizing errorsBrittle with age, lose luster, heavier than other plastic frames

90
Q

Propianate characteristics:

A

hypoallergenic yes very hypoallergeniclightweight yes very hypoallergenicstrong noflexible yes

91
Q

What are some advantage/disadvantages of Propionate?

A

less “dulling” food flex, verylightweight and hypoallergenicnot as common a zyl,heat and solventsensitive.lens size has to be exact

92
Q

Optyl characteristics

A

Thermoelastichypoallergenic yeslightweight yesstrong yesflexible yes

93
Q

Optyl advantages/disadvantages

A

very light, excellent shape retetion, hypo-allergenic, very heat and solvent resistantDifficult adjustments that require heat, will not shrink

94
Q

Aluminum characteristics

A

hypoallergenic nolightweight yesstrong yesflexible nocorrosion resistantyes

95
Q

Aluminum advantages/disadvantages

A

good to very good resistance, high luster, lightlens often have “gapping”, complicated manufacturing with rivets

96
Q

Monel characteristics

A

most widely used, has nickel (and copper, etc)hypoallergenic nolightweight nostrong noflexible highly flexiblecorrosion resistantyes (when plated)

97
Q

Monel advanteges

A

Cost-effective and efficient, malleablemedium corrosion resistance unless plated, heavier

98
Q

Titanium characteristics

A

hypoallergenic yeslightweight yesstrong yesflexible nocorrosion resistantyes

99
Q

Titanium pros/cons

A

very light and hard, hypoallergenicvery expensive, not very flexible

100
Q

Flexon characteristics, pros/cons

A

Titanium alloy (Marchon), AKA memory metalhypoallergenic yeslightweight yesstrong yesflexible highly flexible can bend to original shapecorrosion resistantyeshard to adjust, patterns not as available

101
Q

Beryllium,characteristics, pros/cons

A

low-cost alternative to titaniumhypoallergenic nolightweight yesstrong yesflexible yes, but springycorrosion resistantyesgood for salty/acidic patients

102
Q

Stainless steel characteristics, pros/cons

A

steel chromium alloyhypoallergenic yeslightweight yesstrong yesflexible no, springycorrosion-resistant yes

103
Q

Which nosepad is hard and nonflexible?

A

Acetate

104
Q

Which nosepad is flexible, slippery?

A

Vinyl

105
Q

Which nosepad is grippy and sticky?

A

Silicone

Ophthalmic optics 2 (4 decks)

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