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Ophthalmic Optics II > Absorptive Lenses > Flashcards

Absorptive Lenses Flashcards

1
Q

ultraviolet range in nm

A

295nm - 400nm

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2
Q

visible light in nm

A

400nm- 800nm

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3
Q

infrared light in nm

A

800nm- 1200nm

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4
Q

UV-C range in nm

A

100-280 nm

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5
Q

UV-B range in nm

A

280-315 nm

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6
Q

UV-A range in nm

A

315-400 nm

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7
Q

cornea absorbs what % of

  • incident UVC
  • incident UVB
  • incident UVA
A
  • UVC: 100%
  • UVB: 90%
  • 60% incident UVA
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8
Q

the majority of the remaining ____ is absorbed by the lens

A

UVA

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9
Q

does UVA reach the retina?

A

small portion of UVA reaches the retina

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10
Q

how much of the high energy visible light (HEV) passes through the cornea and lens?

A

85-90%

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11
Q

effects of UV absorption of the cornea

A
  • photokeratitis

- pterygia

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12
Q

cataracts from UV-A and UV-B light exposure

A

cortical cataracts: small, 10% increased risk with higher lifetime sunlight exposure, mechanism not fully understood

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13
Q

cataracts from infrared light exposure

A

glass blowers cataract

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14
Q

cataracts from high energy microwave

A

cataracts formed by direct damage to lens fiber cell membranes

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15
Q

retinal light damage is from

A

UV and HEV (photo thermal, photomechanical, photochemical)

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16
Q

what type of light is related to macular degeneration?

A

high energy visible light

17
Q

how can high energy visible light causes macular degeneration?

A
  • short wavelength and blue light cause significant oxidative stress to the RPE
  • need further studies and clinical trials to understand fully
18
Q

3 things infrared radiation

A
  • absorption of high energy IR radiation causes vibrational changes in molecules
  • increased temperature on tissue causes denaturation of proteins
  • results in loss of function of proteins and enzymes critical to metabolic processes
19
Q

effects of infrared radiation on cornea, iris, lens, retina

A
  • cornea: corneal burns
  • iris: de-pigmentation & atrophy
  • lens: glass blower’s cataract
  • retina: burns
20
Q

total light transmission through a lens=

A

incident light (I) - (reflection + absorption)

21
Q

medications causing increase sensitivity

A
  • tetracycline
  • sulfa drugs
  • birth control
  • diuretics
  • tranquilizers
22
Q

protection from UV can be from:

A

absorptive- metal oxide

or reflective- reflective coating

23
Q

discomfort glare causes:

A

discomfort but does not affect visual performance

24
Q

disability glare (Veiling glare)

A

decrease in contrast causing decrease visibility or resolution such as cataracts, UV absorption by the lens, and cornea scarring

25
Q

dazzling glare can cause

A

photophobia

26
Q

how do glare control lenses work?

A

block short wavelengths to increase contrast

27
Q

disadvantages of glare control lenses?

A

may have an effect on color vision, depending on amount of visible spectrum that is absorbed by the lens

28
Q

glass photochromic lens contain

A

silver halide, breaks into silver and halogen when activated by UV, rebinds to silver after exposure to UV stopped

29
Q

plastic photochromic lenses contain

A

indolino spiroazines (ISN), this material penetrates the lens surface at about 150 microns, when activated ISN changes structure and darkens- reduces transmittance

30
Q

what does AR coating reduce and increase?

A

reduces reflection

increases light transmission through the lens

31
Q

the ___ the index, the more light is reflected off the surfaces and therefore the less light transmitted

A

higher

32
Q

labert’s law of absorption

A

same % of light is absorbed regardless of intensity of incident light through homogenous substance

33
Q

the intensity of transmitted light varies exponentially as a function of

A

the length of the light path in the absorbing media

Ophthalmic Optics II (8 decks)

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