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UCL Medical Retina 2 > Unit 3 - Imaging > Flashcards

Unit 3 - Imaging Flashcards

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USMLE® Step 1 flashcards
1
Q

What are top 3 most reflective layers on OCT?

A
  1. RNFL
  2. Ellipsoid zone (junction between inner segment and outer segments)
  3. RPE/Bruchs
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2
Q

Current OCT instruments use which wavelength of what type of light?

A

IR light of about 840nm

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3
Q

What absorbs light between 200-600nm?

A

haemoglobin

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4
Q

What absorbs light above 1000nm?

A

Water in tissue

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5
Q

What does doppler OCT measure?

A

Velocity of blood flow in eye

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6
Q

What spacing are the ETDRS grids?

A

1,3,6mm

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7
Q

What is the average retinal thickness?

A

250um

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8
Q

Which people tend to have thinner retinas?

A
  1. Myopes
  2. Older patients
  3. Women
  4. African patients
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9
Q

What drug may cause IRF?

A

Latanoprost

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10
Q

What do vitelliform lesions look like on OCT?

A

Yellow, round elevated lesions below neurosensory retina

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11
Q

What do pseudcysts look like on OCT and what causes them?

A

Round or oval cystic spaces

Represent a loss of muller cells and may be a precursor to a macula hole

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12
Q

What do tubulations look like on OCT?

A

round/oval lesions surrounded by hyperflectivity caused by a rearrangement of the photoreceptor layer in response to injury.

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13
Q

What colour light do you use to take RNFL photos?

A

Short wavelength i.e. blue

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14
Q

What colour light do you use to take choroid photos?

A

Long wavelength i.e. red

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15
Q

What blocks green light?

A

Pigment in RPE, useful for viewing nerve fibre layer, diabetic retinopathy, ERMs and PED.

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16
Q

What size are microanuerysms?

A

30um

17
Q

When is an FFA better than an OCTA?

A

With larger PED

18
Q

What are the pros of OCTA?

A
  1. Quick, non-invasive
  2. Can see different layers
  3. Good sensitivity and specificity
  4. Can help differentiate immature, mature and hypermature lesions
19
Q

What are the cons of OCTA?

A

Don’t work well with PED
Extreme flow patterns may be undetected
Can be noisy and difficult to spot leak

20
Q

What are the cons of FFA?

A
  1. Labour intensive
  2. Uncomfortable for patient
  3. Danger of anaphylaxis
  4. Side effects of Fluorescein
  5. Can’t see different layers
21
Q

What are the side effects of fluorescein?

A

Flushing
Erythema
Nausea
Vomiting
Hypersensitivity reacion
Anaphylactic shock and death

22
Q

How is a projection artefact caused in OCTA?

A

Light is reflected at a deeper level than it should be causes blood flow signals where they should be absent.

23
Q

What do motion artefacts look like on OCTA?

A

Horizontal white lines

24
Q

What can cause areas that look like non-perfusion on OCTA?

A

Media opacities

25
Q

What is the best OCTA scan for looking at nAMD?

A

6 x 6mm

26
Q

When would you use a 12X12 OCTa scan?

A

RVO and DR
Covers macula and just beyond arcades

27
Q

What are the two clasification systems for CNVM?

A

One based on OCT images, Type 1, type 2 and type 3
One based on FFA images, Classic, occult

28
Q

Where do Type 1 CNVM form?

A

Sub-RPE

29
Q

Where do Type 3 CNVM form?

A

Within retina

30
Q

What are outer retinal corrugations?

A

Undulating sheets of hyperreflective material above Bruchs

31
Q

What is the difference between drusen and outer retinal corrugations?

A

Drusen sit within Bruchs

32
Q

What are the two types of focal choroidal excavation?

A

Conforming (no separation between posterior retina and RPE) and non-conforming (separation between posterior retina and RPE)

33
Q

Who does focal choroidal excavation effect most?

A

Myopic asian males

34
Q

What other conditions are associated with FCE ?

A

ERM, CSR, dry AMD, PCV,

35
Q

What percentage of FCE may develop CNVM?

A

10%

36
Q

In FAF what lesions will show increased flurophore?

A

Lipofuscin related i.e. Bests, Stargardts, Pattern dystrophy, CSCR
Other fluorophores i.e. disc drusen, astryocyic hamatomas

37
Q

When do you get reduced fluorescence in FAF?

A

Loss of lipofuscin, reduced RPE metabolic demand

UCL Medical Retina 2 (30 decks)

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