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Ophth. Optics II > Absorptive Lenses > Flashcards

Absorptive Lenses Flashcards

1
Q

these are lenses designed to prevent wavelengths from entering the eye reduces the intensity of certain wavelengths that do enter the eye

A

absorptive lenses

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2
Q

which UV rays are closest to the visible spectrum

A

UV-A

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3
Q

what is the range of the visible spectrum

A

380nm- 760nm

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4
Q

Which UV has spectrum of 380-320 nm

A

UV-A

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5
Q

which UV has spectrum of 320-290 nm

A

UV-B

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6
Q

which UV has spectrum of 290-200 nm

A

UV-C

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7
Q

what is the infrared spectrum

A

760 nm - 1 mm

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8
Q

which lenses transmit all light roughly equally

A

crown glass- clear

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9
Q

what percentage of light is transmitted and why

A

92% bc of light reflection from the front and back of the lens , which is 4%

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10
Q

which lenses cause the transmittance curve to shift to the right ; better UV blocker than crown glass but not optimal

A

CR- 39 clear

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11
Q

which lens is an excellent UV blocker

A

polycarbonate

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12
Q

what three things happens when light strikes a lens

A

reflection, absorption, and transmission

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13
Q

reflection equation = amt of light reflection by a lens surface

A

I(r) =( ( n- n)^2/ ( n + n) ^2 ) x (I)
n* = index of lens
I(r) incident light that strikes front of lens -> complete example problem on slide 18

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14
Q

what is I on the front and back surface of the lens

A

I is 1 on the front surface and 0.96 on the back surface because not all the light made it through

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15
Q

T or F: transmission= incident light - reflection from surface - absorption- reflection from back surface

A

T

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16
Q

as index of refraction goes up…

A

reflectance goes up

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17
Q

this law states that for an absorptive material, layers of equal thickness absorb equal quantities of light regardless of the intensity of light

A

lamberts law of absorption -> example slide 22

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18
Q

T or F: transmission = I ( incident light ) x q ( number of thicknesses)

A

T -> ex slide 24

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19
Q

What is the ultimate transmission

A

when light passes through a number of lenses

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20
Q

how is the ultimate transmission found

A

by multiplying separate transmission of each of the lenses T= T1 x T2 x T3 example slide 28

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21
Q

what is the term used for the reciprocal of transmission

A

opacity

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22
Q

T or F: the equation for opacity is O = 1/ T

A

T ; ie. slide 30

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23
Q

how is ultimate opacity

A

when light passes through a number of lenses , it can be found by multiplying the separate opacities of each of the lenses O= O1 x O2 x O3 -> ie slide 32

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24
Q

T or F: optical density is Optical Density = -log Transmission
D = -log T

A

T : ie slide 34

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25
Q

which types of lenses acts as a filter and can be uniform or neutral ; also which can be selective

A

absorptive lenses

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26
Q

which type of absorptive lens has the color imparted to the lens by the addition of an absorptive substance

A

tinted solid glass lenses

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27
Q

which type of absorptive lens has a thin metallic oxide that is deposited on the surface of the lens ; usually the back surface ; requires high temps

A

glass lenses with surface coatings

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28
Q

these lenses are tinted by dipping into a dye; dye penetrates to a uniform depth

A

tinted plastic lenses

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29
Q

which tint color has no color distortion for wearer ; and is used to try and negate poor indoor lighting conditions

A

pink

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30
Q

which tint is used as a bold fashion color

A

red

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31
Q

which tint is possibly used for shooting glasses, night driving, and poor visibility , enhances contrast of targets against the sky

A

yellow

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32
Q

which color approximates color sensitivity curve of the human eye ; increases depth perception , maybe golf?

A

green

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33
Q

which tint is popular for sun lenses and has higher absorption of shorter visible wavelengths

A

Brown

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34
Q

most popular tint for sun protection ; colors seen in natural state

A

gray

35
Q

what is normal transmission for sun lenses

A

15-30%

36
Q

what happens if transmission is too high

A

may not hep average wearer in full sunlight

37
Q

what happens if transmission is too low

A

results in visual acuity reduction in dimly lit conditions

38
Q

how do photochromic lenses work

A

glass contains silver halide crystals -> lenses darken when exposed to long wavelength UV radiation -> UV transforms silver halide crystals into silver and halogen atoms ; darkening rate is temperature dependent

39
Q

what are the different types of photochromic glass lenses

A

photogray II, photogray Extra, photobrown extra, photosun II

40
Q

which lenses relive glare for pts with severe light intensity and filter out shorter ( blue ) wavelengths

A

corning photochromic filter lenses- glass

41
Q

what compounds are used to produce the photochromic effect in plastic

A

spiropyrans

42
Q

what type of technology is corning sunsensors and rodenstock

A

in-mass technology

43
Q

what type of technology is transitions

A

imbibed technology

44
Q

some features of this technology is that molecules never wear out; darkens up to 50 % in the car, scratches don’t affect performance; exterior 1.5 mm of lens activated preventing uneven darkenign

A

in-mass

45
Q

features of this technology include darkens consistently across the lens regardless of Rx; available in wide range of material and designs

A

imbibed technology

46
Q

this type of transitions is a photochromic product for all around; balance between outdoor darkness and indoor; doesn’t change behind car windshield; no polarization ; colors are gray, brown, and graphite green

A

transitions VII

47
Q

what type of transitions is for pts. in bright sunny conditions; has superior outdoor darkness with a slight indoor tint; moderate activation behind a car windshield ; no polarization; colors are gray, brown, or green

A

transitions XTRActive

48
Q

what type of transitions is a photochromic product with variable polarization as the lens darkens; darkens with increasing polarization outdoors; dark outdoors and clear indoors ; doesn’t change behind a car windshield and clear to gray only

A

transitions vantage

49
Q

what type of trans is designed for pts that spend more time in bright sunlight ; designed to be worn outdoors ; multiple color options

A

transitions adaptive

50
Q

what type of lenses have new photochromic technology . have better clearing speed; better fatigue resistance and can be tinted

A

photofusion lenses

51
Q

which photochromic lenses claims they are the second largest selling photochromic on the market

A

corning sunsensor

52
Q

what are the Photochromatic plastic fashion tints

A

splitz (sola) changeable fashion tint); and solera (invicta) darkens into a darker fashion tint outdoors

53
Q

which Photochromatic lenses go from clear to brilliant saturated shades

A

beloptix 1.60 polarized

54
Q

T or F; transitions optical is partnering with motorcycle safety equipment manufacturers to produce face shields and visors

A

T

55
Q

what diff face shields is transitions making to be put on helmets

A

bell transitions face shield, laser lumino trans, and SHOEI trans adaptvie face shield

56
Q

what is bright light that interferes with optimal vision, produces discomfort

A

glare

57
Q

what are the diff types of glare

A

distracting , discomfort, disability, and reflected

58
Q

this type of glare caused by lens reflections

A

distracting

59
Q

this type of glare is sensation of irritation or pain from sources of light ; light doesn’t interfere with resolution

A

discomfort

60
Q

this type of glare causes objects to appear to have lower contrast than they would if there were no glare; it increases the brightness of the background and lowers the brightness of the object thereby interfering with the resolution ie. turning on the room lights while trying to watch a slideshow

A

disability

61
Q

T or F: light sources with the central 10 degrees of the visual field contribute to disability glare

A

T

62
Q

this type of glare is also know as blinding glare ; glare caused by reflected light sources

A

reflected glare

63
Q

how are polarized lenses manufactured

A

suspending polarized film within the lens mold and casting the lens with the film in place

64
Q

what are the two axes of a polarizing filter

A

absorption axis and a transmission axis

65
Q

this axis blocks all polarized light incident at that axis

A

absorption axis

66
Q

this axis transmits all polarized light incident at that axis

A

transmission axis

67
Q

how do the axes have to be oriented to each other for polarization

A

perpendicular

68
Q

this type of lens eliminates specularly reflected horizontal polarized light; improves VA and restores the natural balance of light intensities; helpful for motorists, fishermen, and skiers

A

polarizing lenses

69
Q

what are materials that best polarize light ; they are nonconductors such as glass, pavement, sand, and snow

A

dielectrics

70
Q

light reflected from a dielectric is completely polarized at a specific angle of incidence called

A

Brewsters Angle

71
Q

What is the equation for Brewsters Angle

A

tan I= n*
n*= index of medium to which the light is incident
I= angle of incidence for which the reflected light is most completely polarized example on slide 90

72
Q

T or F: Polarized lenses reflect horizontal light waves and admit vertical vibrating light waves

A

T

73
Q

what is a well know company for producing polarized resin lenses

A

NuPolar Lenses

74
Q

this film is located .4 to .8 mm from the lens front surface ; polarizing axis alignment is critical ; tolerance is 3 degrees

A

nupolar lenses

75
Q

this law determines the intensity of light that passes through two perfect polarizers ( 2nd polarizer is called an analyzer)

A

Malus Law: Io = I cos^ 2 θ

theta; angle between transmission axis of first polarizer ( lights initial plane of polarization) and the transmission axis of the second polarizer
I= intensity of the light
I(o)= light passing through two polarizer series; example slide 102

76
Q

according to Malus Law, if the two polarizers are 90 degrees apart, the polarizers are crossed , is light transmitted?

A

no

77
Q

according to Malus Law, if the two polarizers are coincident ( transmission axes aligned,) the polarizers are uncrossed and how much light is transmitted

A

100 %

78
Q

what are some negatives about glare

A

glare from natural sunlight can be visually debilitating; glare from natural sunlight has contr. to aviation accidents

79
Q

pros about appropriate aviation suns

A

free from distortions and imperfections; transmit 15 % overall light ; don’t alter color perception; employ larger lenses in a wrap around design

80
Q

these sunglasses are not recommended for aviation bc they reduce the visibility of instruments in the cockpit; interfere with visibility through an aircraft windscreen ; mask the sparkle of light that reflects off shiny surfaces of other planes wings etc

A

polaroid sunglasses

81
Q

what can be added to the lens that provides advantage of blocking UVA, UVB, and glare , and HEV radiation

A

melanin

82
Q

what are two types of combination lenses

A

transitions drivewear and julbo falcon lens

83
Q

this type of lens have trans photochromic technology plus; nupolar polarization

A

drivewear lens

84
Q

this is a plastic photochromic lens ; reacts only to visible light ; darkness not affectd by windshield ; not affected by temp. ; polarized lens; AR coated

A

julbo eyewears falcon lens

Ophth. Optics II (7 decks)

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