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Optics BLOCK 4 > Intraocular Light Scatter II > Flashcards

Intraocular Light Scatter II Flashcards

1
Q

What are the two refractive surfaces of the eye?

A

Cornea and lens

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2
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
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3
Q

What parts of the eye cause forward scattering?

A

Cornea, sclera and iris, lens, vitreous humor

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4
Q

What parts of the eye cause backward scattering?

A

Retina

This gives us access to understand the function of the eye

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5
Q

What does scleral thinning cause?

A

Bluish appearance due to rayleigh scattering

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6
Q

Corneal light scattering is _______ for all healthy eyes, and for all ages

A

Identical (constant)

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7
Q

Corneal transmittance is _________ dependent

A

Wavelength

Rayleigh scattering

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8
Q

When the wavelength increases, the corneal transmittance _________

A

Increases

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9
Q

Contact lens wearers experience a _______________

A

Significantly higher light scatter

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10
Q

On average, contact lens scatter is ___________ higher than spectacle wearers

A

0.22 log units

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11
Q

Corneal light scatter may increase __________

A

Post laser refractive surgery

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12
Q

Light scatter in the cornea

A
  • constant in all healthy eyes
  • wavelength dependent
  • increases with contacts and corrective surgery
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13
Q

For radial keratotomy (RK) mean stray light increases by a factor of ______ in eyes with 4mm pupil and a factor of _________for 8mm pupil.

A

1.4

2 (0.3 log units)

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14
Q

Photorefractice keratotomy (PRK) does what for light scattering in the cornea?

A

Corneal backscattering of light, which correlates with visible haze, is significantly stronger after PRK

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15
Q

Laser assisted in situ keratomileusis (LASIK) does what for corneal light scatter?

A

Epithelial ingrowth after LASIK can cause an increase in straylight

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16
Q

Corneal refractive therapy (CRT) and corneal light scatter

A

Reported decreased scatter in the follow ups

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17
Q

Which refractive procedure reduces decreased scatter in the cornea?

A

CRT

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18
Q

What does a pigmented iris do to scattering?

A

Decreases it

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19
Q

As angle of scatter increases, scatter ________ in blue eyes a lot

A

Increases

20
Q

Are the scare and iris opaque?

A

Not totally, some pigment is here as well as in the iris

21
Q

What do the sclera and iris due since they do have pigment

A

Diffusely transmit long wavelengths due to the color of pigments in the scleral wall and iris

22
Q

For a dark brown eye of pigmented individuals, transmission is lower by _________

A

Two orders of magnitude

23
Q

The amount of scatterin/stray light in the eye depends also on ________

A

Pigmentation of the fundus

24
Q

Fundus has a stronger reflectance of __________ wavelengths due to the pigments and the blood

A

Longer (red)

25
Q

Blue eyes cause greater what?

A

Back scattering of light from fundus and more light transmission through the eye wall

26
Q

What pupil size has the highest scatter?

A

2-3 mm

27
Q

What happens to scatter in pupils with 4-10mm pupils?

A

Scatter remains the same

28
Q

Light scattering by the crystalline lens and age

A

Increases significantly with age and much higher for cataracts

  • increases by 2x by age of 65
  • increases by 3x by age 77
29
Q

Results of water absorption and subsequent phase separation within the IOL matrix and are clinically observed in almost all types of IOL material, including hydrophobic and hydrophilic acrylics, silicone, and PMMA

A

Glistening

30
Q

What kind of lens has less scatter than a normal healthy eye

A

Monofocal

31
Q

What does glistening cause

A

Stronger glare, especially when driving

32
Q

What does scatter reduce?

A

-contrast and VA

33
Q

Introduced IOLS to reduce the amount of blue light transmission in the eye

A

Blue light blocker

34
Q

Light scatter is stronger with _____

A

Blue

35
Q

Benefits of blue light blocker

A
  • drastically reduces light scatter
  • blocks blue iChat harmful to retina
  • reduce aberrations of the eye
  • do not affect VA, CS, and color vision
36
Q

What are some potential side effects of reduction in blue light?

A

Color vision disturbance
Decreased scoptopic sensitivity
-sleep-wake timing disruption

37
Q

Effects of light scattering: cornea

A
  • constant

- forward scattering

38
Q

Effects of light scattering: sclera and iris

A
  • pigmentation

- diffuse transmission of red

39
Q

Effects of light scattering: lens

A
  • forward light scattering

- age and cataract dependent

40
Q

Effect of light scattering: vitreous

A
  • forward scattering

- age

41
Q

Effect of light scattering: retina

A
  • backward scattering
  • pigmentation
  • fundus reflectance
42
Q

Radiation of sharp needles of light that is perceived subjectively around a bright point light source that originates from light scattering by small particles

A

Ciliary corona

43
Q

Color banded, much like the rainbow, perceived surrounding a bright spot of light at a mean distance of 3 degree radius.

A

Lenticular halo

44
Q

Originates from the fibrous structure of the eye lens

A

Lenticular halo

45
Q

The lens fibers form a diffraction grating, arranged in a circular fashion, much like the spokes of a wagon wheel

A

Lenticular halo

46
Q

Appears only for larger pupil sizes, depending on the subject

A

Lenticular halo

Optics BLOCK 4 (15 decks)

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