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Optics Block 8 > Posterior Segment Imaging > Flashcards

Posterior Segment Imaging Flashcards

1
Q

What is the nyquist limit

A

60

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2
Q

What happens to the nyquist limit if you get rid of optics

A

It doubles to 120

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3
Q

After the nyquist is at 120, what is the limiting factor

A

Neural

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4
Q

Three major conventional retinal imaging tools

A
  • fundus camera
  • scanning laser ophthalmoscope (SLO)
  • optical coherence tomography (OCT)
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5
Q

What is the problem with ground based terelcsopes

A

Atmospheric turbulence

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6
Q

How do you get around atmospheric turbulence without putting the telescope into satellite

A

AO based telescope

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7
Q

How does AO based telescope bypass the atmospheric turbulence

A

Shack hartman sends WF to deformable mirror and the mirror will deform its surface and can take the shape of the deformed wavefront and give us a plane wavefront that has not aberrations

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8
Q

The ability to image cones at high resultion with AO opened a window for what

A

To examine both normal and abnormal processes in the retina

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9
Q

What happens when you correct higher order aberrations

A

Produced a modest improvement in VA and contrast sensitivity in the normal eye

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10
Q

What does using an adaptive optics imagin system do when looking at the back of the eye

A

Can learn where the rods and cones are/are not and where they are dense or not

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11
Q

How do you tell the color cones apart

A

Bleach them

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12
Q

L cones

A

Red

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13
Q

M cones

A

Green

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14
Q

S cones

A

Blue

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15
Q

How can individual cones be characterized by their sensitivity to long, medium, or short wavelength light, according to the cone opsin it contains

A

By combining AO imaging with retina densitometry

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16
Q

When look at an image of rods and cones, which ones are green cones (M cones)

A

Brighter looking ones

17
Q

When looking at an image of the rods and cones, what are the darker cones

A

Blue cones

18
Q

Ratio of L and M cones across individuals

A

Highly variable without affecting VAs

19
Q

Proportion of S cones amongst individuals

A

The proportion of S cones is relatively constant across eyes (3.9-6.6%)

20
Q

Why cone opsin is constant across individuals

A

S cones

21
Q

What opened a crucial window to examine both normal and abnormal processes in the retina

A

The ability to image cones at high resolution with AO

22
Q

Cone mosaics of single gene dichromats

A

Appear completely normal despite the fact that they have two instead of the usual three cone photopigments

23
Q

What happens when someone has no L cons

A

M cones try to occupy the space, sometimes its just left unoccupied

24
Q

When a dichromat is missing 1/3 of their foveal cones, how does this affect VA

A

They are normal, indicating that adaptive optics imaging can detect retinal degeneration well before conventional clinical tests

25
Q

Where are the PR larger, in the center or peripheral

A

Peripheral

26
Q

What is the main advantage afforded by the SLO over traditional imaging

A
  • improved efficiency in light collection (through the use of more sensitive detectors)
  • video rate imaging capabilities
27
Q

Benefit of confocal detection is 2 fold

A
  • resulting images have higher contrast

- through axial scanning of the foca spot, axial slices of the retina can be obtained with 300mm resolution

28
Q

AOSLO images of retinal vasculature

A

AO combined with fluorescein angiography allows imaging of even the fine structure of the retinal cap bed

29
Q

What does AOSLO images of retinal vasculature detect

A

Direction of blood flow and the velocity within the caps

30
Q

The retinal image is conveyed to the brain through an array of

A

17 or more parallel ganglion cell pathways

31
Q

diabetic retinopathy and adaptive optics

A

Can see how the vessels are leaking

32
Q

Imaging RPE with adaptive optics

A
  • maintains the photoreceptors
  • ARMD, RP, Stargardts
  • AO reflectance imaging makes it possible to image the RPE mosaic in living human eyes in which the PR layer is instant, by taking advantage of the autoflourescence properties of lipofuschin in the RPE
33
Q

AO OCT

A

Lateral and axial resolution

-can go to each layer and look at subcellular layer

34
Q

Applications of AO-OCT

A
  • ARMD
  • glaucoma
  • diabetic retinopathy
  • stem cell treatment of degenerative disorders of the retina

Optics Block 8 (9 decks)

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