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Flashcards in Intraocular Scatter 1 Deck (60):
1

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

Tyndall scattering (colloidal particle scattering)

2

What does tyndall scattering act like?

More like rayleigh

3

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

Transparent particles

4

Tyndall scattering is _______ dependent scattering (almost)

Wavelength

5

Scattering profile of tyndall scattering

Scattering in more directions, not just forwards and back

6

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

Absorption. More like rayleigh

7

Tyndall scattering in opal

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

8

What gives blue eyes there blue appearance?

Tyndall scattering in the iris stroma

9

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

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

10

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

Shorter

11

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

Structural

12

Why do albinos have red eyes?

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

13

The incoherent scattering depends on the ________ size

Particles

14

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

Mie

15

What causes scattering in mie scattering?

Reflection and refraction Caucasus scattering

16

Direction of scattering mie scattering

Forward

17

Mie scattering is _______ independent

Wavelength

18

Example of mie scattering

Whiteness of the clouds

19

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

Tyndall

20

What causes the scattering in tyndalll

Interior wave effects causes scattering (diffraction)

21

Direction of scattering in tyndall

Spread light out in more direction

22

Tyndall scattering is ________ dependent

Wavelength

23

Examples of tyndall scattering

Halos seen though a fogged up car window

24

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

Rayleigh

25

What causes scattering in rayleigh

Dipole re-radiation causes scattering

26

What direction does rayleigh scattering have?

All directions

27

What kind of wavelength dependence does rayleigh scattering have?

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

28

Example of rayleigh scattering

Blue sky

29

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

Mie

30

What scattering scatters roughly equally in all directions

Rayleigh

31

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

Polarization

32

Orange sunset is what type of scattering?

Multiple

33

Green flash at sunset

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

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

Coherent scattering

35

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

Smaller

36

Each particle acts as a _____ for the coherent scattered waves

Source

37

Scattered waves propagate _______ and overlap in coherent

Outward

38

Coherent scattering acts as a

Diffraction grating

39

Many coherent scattered waves interfere destructively in ______ directions

Most

40

Many coherent scattered waves interfere constructively in _____ directions

Two

41

Constructive coherent scattering in 2 directions

-Parallel to incident light (forward scatter)
-refract relative to incident wave (phase shifted)

42

Light scatter leads to deleterious visual effects like

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

43

Sources of ocular scatter

-cornea
-sclera and iris
-lens
-vitreous humor
- retina

44

Forward scattering (FWS)

Light going into the eye

45

Backward scattering (BWS)

Light reflecting back from the fundus

46

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

Backward

47

______ light scatter is studied in vitro in human donor lenses

Forward

48

What is BWS used for

Dx

49

What is FWS used for

Function of vision, human donor lenses

50

What does the corneal endothelium do

Pumps excess water out of the cornea into the aqueous humor

51

Reasoned for scattering in cornea

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

52

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

Larger
Mie scattering

53

Due to ___________, sclera appears whitish

Large particle incoherent forward scattering

54

Sclera thinning

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

55

Melanin and scleral function

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

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

Yellow

Functional effect

57

Cataract and scattering

Fluid pools

58

Floaters

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

59

Retina scatters light as much as the ______

Cornea
1/3 bws

60

How does rental scattering increase

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)