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Ophthalmic Optics > Spectacle Transmission > Flashcards

Spectacle Transmission Flashcards

1
Q

1-4
A-D
to denote color density
as number ascends…_

A

transmission reduces

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2
Q

high plus or minus lenses have different transmission throughout lens; darker where _

A

thicker

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3
Q

visible spectrum:

A

380-760 nm

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4
Q

much UV and IR light doesn’t reach retina; it’s absorbed by:

A

cornea, aqueous humor, lens, vitreous humor

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5
Q

less than 400 nm is considered:

what end is most harmful:

A

UV radiation

shorter wavelengths

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6
Q

ocular damage caused by UV:

A

high burst

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7
Q

a single dose of high level UV radiation

A

Welders burn

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8
Q

excessive exposure to UV causes:

A

photokeratitis (snow blindness)

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9
Q

it takes _ hrs after a burn to feel pain

-heals in _ hrs

A

6

6 to 24

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10
Q

long term low dose UV results in:

A

cataracts

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11
Q

_ are at risk for retinal problems due to UV

A

aphakic (macular degeneration)

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12
Q

IOLs are _

A

UV absorbing

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13
Q

best method to reduce UV related eye disease is:

A

sunglasses early in life

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14
Q

only lens materially that inherently does not come with UV filter?
can do what?

A

CR-39

UV dye

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15
Q

good quality polarizing lenses filter _

A

UV radiation

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16
Q

Do photochromic lenses protect against UV light?

A

yes - in their darkened state

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17
Q

glare control lenses block _

A

short blue wavelengths

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18
Q

_ measure UV absorption

A

photometers

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19
Q

How to test if lens absorbs UV?

A

place test lens over an unedged plastic photochromic lens and expose to sunlight - if photochromic darkens, test lens does not absorb it all

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20
Q

frame selection for UV:
_ lens area
fits _
_ style

A

large
close to face
wrap

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21
Q

when UV radiation combines with blue light and IR, causes lens opacification called:

A

glass blower’s cataracts

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22
Q

sources of IR radiation:

A

molten substance (glass, metal)
arc lamps
IR lamps

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23
Q

lenses that block IR

A

NoIO

IREX

24
Q

transmission for sunglasses is:

A

15-30%

25
Q

sunglasses that transmit less than 15% may present problems because of _

A

reflected glare from back surface (back surface AR fixes this)

26
Q

according to ANSI standards, sunglasses used for driving should not be darker than:

A

8%

27
Q

special purpose 3% transmission may be used for:

A

rock climbing, beach, skiing

28
Q

single exposure to ordinary bright light for 2-3 hours caused dark adaptation to start _ minutes later

caused normal night vision to be delayed by _

A

10

several hours

29
Q

dark adaptation loss can be prevented with sunglasses that have transmission between:

A

10-15%

30
Q 
normal 20/20
through glass windshield: _
through 82% transmission pink lenses: _
green tinted windshield: _
together: _
A

20/32
20/40
20/46
20/60

31
Q

Does a light tint reduce glare at night? Use what?

A

no (they do reduce internal reflections)

AR - increase transmission, increase contrast sensitivity

32
Q

crown glass and plastic transmit _%

A

92

33
Q

pink lens benefit?

A

transmit light uniformly (no color distortion)

reduces glare because it reduces internal reflections

34
Q

yellow are advocated for _ driving because they enhance contrast

A

fog/haze, night driving

35
Q

most common color used in germany, higher absorption in shorter wavelengths like with yellow lenses

A

brown

36
Q

lens color that has a transmission curve close to color sensitivity of human eye, good UV and IR too

A

green

37
Q

green is a very _ tint

A

comfortable

38
Q

most popular color for sun protection

A

gray

39
Q

gray offers _ transmission

A

uniform

40
Q

best lens color for color vision deficient patients

A

gray

41
Q

4 categories for sunglasses

A
  1. cosmetic
  2. general purpose
  3. very dark
  4. strongly colored (selective filtration)
42
Q

color deficient individuals cannot discriminate red and green traffic signals through _ lens color

A

brown

43
Q

tinting plastic lenses:
longer dip = _
_ color

A

darker

uniform

44
Q

lenses are darker in the upper portion of lens

A

gradient tinting

45
Q

_ does not tint at all, all tint is absorbed by scratch coating

A

polycarb

46
Q

advantage of color coating lenses:

A

uniform density regardless of thickness

47
Q

color coating lenses results in smoothness of its _

A

transmission curve

48
Q

Do internally tinted or color coating lenses allow more transmission?

A

color coating

49
Q

sunglass wearers can experience reflections on back surface from behind during the day, what would fix this?

A

back surface AR

50
Q

reflections on front surface from behind is noticeable at night from _, results in _

A

bright light source from behind, ghost images

51
Q

adjustments that can alleviate ghost images: (2)

A

pantoscopic
faceform
(neither eliminate)

52
Q

regardless of source, _ reduce ALL reflections

A

AR coatings

53
Q

mirrors are applied just like _

A

AR coatings

54
Q

mirror coatings _ transmission due to high amount of reflections, what %

A

reduce (by 15%)

55
Q

mirrors can be used in conjunction with _ to provide extra protection from intense sunlight

A

tints

56
Q

4 types of mirror lenses:

A
  1. full mirrors
  2. gradient mirrors
  3. double mirrors
  4. flash coatings (just a hint)

Ophthalmic Optics (16 decks)

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