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Optics BLOCK 4 > Intraocular Scatter 1 > Flashcards

Intraocular Scatter 1 Flashcards

1
Q

When the scattering particles size is about the same size as the wavelength of light

A

Tyndall scattering (colloidal particle scattering)

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2
Q

What does tyndall scattering act like?

A

More like rayleigh

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3
Q

When ____________ are about the size of a wavelength wave effects result in tyndall scattering

A

Transparent particles

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4
Q

Tyndall scattering is _______ dependent scattering (almost)

A

Wavelength

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5
Q

Scattering profile of tyndall scattering

A

Scattering in more directions, not just forwards and back

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6
Q

There is no dramatic changes due to the _____ during tyndall scattering

A

Absorption. More like rayleigh

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7
Q

Tyndall scattering in opal

A

Tyndall scattering at these in-homogeneities leads to a bluish color in reflected light

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8
Q

What gives blue eyes there blue appearance?

A

Tyndall scattering in the iris stroma

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9
Q

Why does some of the light scatter back out of the eye in blue eyed people

A

In the absence of melanin, the translucent stroma scatter some of the light back out of the eye

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10
Q

Tyndall scattering in a blue takes place to a greater extent at the _____ wavelengths and it viewed against the dark background of the iris pigmented epithelium

A

Shorter

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11
Q

The blue iris is an example of a _________ color, unlike a pigmented color

A

Structural

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12
Q

Why do albinos have red eyes?

A

They do not produce melanin. Their eyes color is red because the blood vessels behind the eyes are visible

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13
Q

The incoherent scattering depends on the ________ size

A

Particles

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14
Q

Is there is a smaller wavelength, what kind of scattering?

A

Mie

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15
Q

What causes scattering in mie scattering?

A

Reflection and refraction Caucasus scattering

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16
Q

Direction of scattering mie scattering

A

Forward

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17
Q

Mie scattering is _______ independent

A

Wavelength

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18
Q

Example of mie scattering

A

Whiteness of the clouds

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19
Q

What kind of scattering has particle size equal to the wavelength of light

A

Tyndall

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20
Q

What causes the scattering in tyndalll

A

Interior wave effects causes scattering (diffraction)

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21
Q

Direction of scattering in tyndall

A

Spread light out in more direction

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22
Q

Tyndall scattering is ________ dependent

A

Wavelength

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23
Q

Examples of tyndall scattering

A

Halos seen though a fogged up car window

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24
Q

If the particle size is smaller than that of the wavelength, what type of scattering?

A

Rayleigh

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25
Q

What causes scattering in rayleigh

A

Dipole re-radiation causes scattering

26
Q

What direction does rayleigh scattering have?

A

All directions

27
Q

What kind of wavelength dependence does rayleigh scattering have?

A

Stronger dependence at shorter wavelengths (blue) than on the longer wavelength

28
Q

Example of rayleigh scattering

A

Blue sky

29
Q

What kind of scattering is responsible for the sky looking whiter near the sun?

A

Mie

30
Q

What scattering scatters roughly equally in all directions

A

Rayleigh

31
Q

When reflected and transmitted light are perpendicular in rayleigh scattering gives strong _________

A

Polarization

32
Q

Orange sunset is what type of scattering?

A

Multiple

33
Q

Green flash at sunset

A

Red and yellow go above the observer, blue goes below and green goes right to the observer. Must be very clear atmosphere with no pollution.

34
Q

When the particles are much closer together than the coherence length of the light, constructive and destructive interference occurs between the waves scattered from different particles

A

Coherent scattering

35
Q

In coherent scattering, particles are much _______ than the wavelength of the light

A

Smaller

36
Q

Each particle acts as a _____ for the coherent scattered waves

A

Source

37
Q

Scattered waves propagate _______ and overlap in coherent

A

Outward

38
Q

Coherent scattering acts as a

A

Diffraction grating

39
Q

Many coherent scattered waves interfere destructively in ______ directions

A

Most

40
Q

Many coherent scattered waves interfere constructively in _____ directions

A

Two

41
Q

Constructive coherent scattering in 2 directions

A
  • Parallel to incident light (forward scatter)

- refract relative to incident wave (phase shifted)

42
Q

Light scatter leads to deleterious visual effects like

A
  • glare while night driving
  • hindrance from low sun during daytime
  • facial recognition problems
  • haziness of vision
  • color and contrast loss
43
Q

Sources of ocular scatter

A
  • cornea
  • sclera and iris
  • lens
  • vitreous humor
  • retina
44
Q

Forward scattering (FWS)

A

Light going into the eye

45
Q

Backward scattering (BWS)

A

Light reflecting back from the fundus

46
Q

Eye is assessed by ______ light scatter, using slit lamp mainly

A

Backward

47
Q

______ light scatter is studied in vitro in human donor lenses

A

Forward

48
Q

What is BWS used for

A

Dx

49
Q

What is FWS used for

A

Function of vision, human donor lenses

50
Q

What does the corneal endothelium do

A

Pumps excess water out of the cornea into the aqueous humor

51
Q

Reasoned for scattering in cornea

A

Loses its transparency and takes on grayish appearance, scar tissue on the cornea

52
Q

The collagen fibers in sclera have ______spacing than the wavelength of light, causing what kind of scattering

A

Larger

Mie scattering

53
Q

Due to ___________, sclera appears whitish

A

Large particle incoherent forward scattering

54
Q

Sclera thinning

A

Fibers get smaller and sclera takes on a bluish color due to rayleigh type scattering
Functional effect

55
Q

Melanin and scleral function

A

Although the function of sclera is to block the light entering the eye, they are not totally opaque. Light can get through sclera depending on the level of pigmentation and density of the structures generating intraocular scattering

Those without melanin may experience more scattering

56
Q

______ pigments in the lens scatter more light (forward scatter)

A

Yellow

Functional effect

57
Q

Cataract and scattering

A

Fluid pools

58
Q

Floaters

A

Coalescing of collagen fibers causes fluid packets, developing a localized scattering, this causes floating specks and threads

59
Q

Retina scatters light as much as the ______

A

Cornea

1/3 bws

60
Q

How does rental scattering increase

A

When blood circulation/supply is interrupted, the retinal integrity is damaged, and edema fluid starts collecting in the nerve fiber layer. This increases retinal light scattering turning the area into milky gray (cotton wool spots)

Optics BLOCK 4 (15 decks)

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