DIS - Ocular Imaging I - Week 3 Flashcards

1
Q

Does digital photography of the eye have non-mydriatic capacity or are dilating drops required?

A

Has non-mydriatic capacity

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2
Q

How large is the field of view typically in digital photography?

A

20-45 degrees

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3
Q

What are mosaics?

A

Multiple fields are aligned by software to get wide field imagery

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4
Q

What cans tereo separation (ie with a mirror) or serial photos give additional information on?

A

Depth information

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5
Q

Briefly define luminescence, fluorescence, and phosphorescence.

A

Luminescence is when electrons in a molecule absorb energy to move to a higher orbit, and then return, releasing a specific longer wavelength
Fluorescence is short term luminescence
Phosphorescence is long term luminescence

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6
Q

What is fundus autofluorescence?

A

Some eye components can produce brief luminescence with illumination

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7
Q

List two ocular compounds that autofluoresce and at what wavelength. For each, describe what one would expect to see with normal vs abnormal ocular health.

A

Lipofuscin at 490nm
-usually builds up with age and disease
Melanin at 790nm
-melanin loss (dark zones) indicates RPE stress/death

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8
Q

Where is lipofuscin produced (2)? What is it?

A

By the lens and dysfunctional RPE

It is undigested residue of cell membranes

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9
Q

What can be used to enhance RNFL definition?

A

Less red light makes the RPE darker and will improve contrast

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10
Q

Describe briefly how fluorescein angiography works.

A

Contrast medium binds to proteins in the blood, especially in blood vessels by the blood-brain barrier

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11
Q

Is contrast media needed with OCTa?

A

No

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12
Q

What is flowmetry?

A

Direct measure of rate of volume of flow

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13
Q

Describe the method for angiography.

A

Indroduce contrast medium into the bloodstream at the arm and monitor appearance in the eye ~15 seconds later
Pattern and time information can be derived

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14
Q

List two common contrast media for the eye and how they work. Note if they extravasate with leaky vessels.

A

Sodium fluorescein - binds to plasma proteins and haemoglobin - extravasates with leaky vessels
Indocyanine green - binds to plasma proteins - doesnt extravasate with leaky vessels, is very large

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15
Q

What is indocyanine green good to study (2) and what does it require (2)?

A

Choroidal vessels or new vessel growth

Requires infrared film and special lenses

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16
Q

Can injected contrast media induce anaphylaxis? What about oral?

A

Yes for injected

No for oral

17
Q

List some common adverse effect sof contrast media.

A

Skin, urine, tissue discolouration

Nausea, dizziness, local skin allergy, phlebitis, skin necrosis, anaphylactic death

18
Q

Are adverse effects common or rare with contrast media? Keeping this in mind, how does this alter its administration in children and younger patients?

A

They are rare but because death is a possibility, oral intake for OCT angiography is preferred in children and younger patients

19
Q

List the fluorescence sequence for the eye following NaFl administration, including seconds (t minus) (5). What stage does oral give?

A
Choroidal - <10 seconds
Arterial - 10-12 seconds
Capillary - 13-15 seconds
Venous - 16-20 seconds
Late (collagen stains) - >30 seconds
Oral intake only gives the late stage
20
Q

Can OCTa give similar resoltution to flurescein angiography?

A

Yes

21
Q

List the two types of fluorescein anomalies give6 examples and what can cause them.

A
Hypofluorescence (dark)
-masking - pigment/blood
-filling defects - vascular defects
Hyperfluorescence (glow)
-window defects - pigment loss
-vascular abnormalities - conformation/structure
-leakage - from blood vessels/RPE
-staining - late stage absorption
22
Q

Keeping the fluorescein anomalies in mind, what should always be taken alongside an angiogram to make sense of the anomalies?

A

A colour photo

23
Q

List three pigments that can cause masking.

A

Xanthophil (macula)
Melanin
Choroidal naevus

24
Q

List two lipofuscin/blood components that can cause masking.

A

Hard drusen

Haemorrhage

25
Q

Can cell hyperplasia cause masking?

A

Yes

26
Q

List two things that can cause filling defects.

A

Retinal/choroidal vascular occlusion

Capillary dropout

27
Q

What is a filling defect?

A

When a blood vessel appears like it is not filled

A colour photo will reveal if this is the case or not

28
Q

What is the mechanism behind a window defect? List two causes.

A

Lack of pigment

  • albino
  • past infection