DIS - Ocular Imaging I - Week 3

Question 1

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

Answer 1

Has non-mydriatic capacity

Question 2

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

Answer 2

20-45 degrees

Question 3

What are mosaics?

Answer 3

Multiple fields are aligned by software to get wide field imagery

Question 4

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

Answer 4

Depth information

Question 5

Briefly define luminescence, fluorescence, and phosphorescence.

Answer 5

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

Question 6

What is fundus autofluorescence?

Answer 6

Some eye components can produce brief luminescence with illumination

Question 7

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.

Answer 7

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

Question 8

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

Answer 8

By the lens and dysfunctional RPE
It is undigested residue of cell membranes

Question 9

What can be used to enhance RNFL definition?

Answer 9

Less red light makes the RPE darker and will improve contrast

Question 10

Describe briefly how fluorescein angiography works.

Answer 10

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

Question 11

Is contrast media needed with OCTa?

Answer 11

No

Question 12

What is flowmetry?

Answer 12

Direct measure of rate of volume of flow

Question 13

Describe the method for angiography.

Answer 13

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

Question 14

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

Answer 14

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

Question 15

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

Answer 15

Choroidal vessels or new vessel growth
Requires infrared film and special lenses

Question 16

Can injected contrast media induce anaphylaxis? What about oral?

Answer 16

Yes for injected
No for oral

Question 17

List some common adverse effect sof contrast media.

Answer 17

Skin, urine, tissue discolouration
Nausea, dizziness, local skin allergy, phlebitis, skin necrosis, anaphylactic death

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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

Question 20

Can OCTa give similar resoltution to flurescein angiography?

Answer 20

Yes

Question 21

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

Answer 21

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

Question 22

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

Answer 22

A colour photo

Question 23

List three pigments that can cause masking.

Answer 23

Xanthophil (macula)
Melanin
Choroidal naevus

Question 24

List two lipofuscin/blood components that can cause masking.

Answer 24

Hard drusen
Haemorrhage

Question 25

Can cell hyperplasia cause masking?

Answer 25

Yes

Question 26

List two things that can cause filling defects.

Answer 26

Retinal/choroidal vascular occlusion
Capillary dropout

Question 27

What is a filling defect?

Answer 27

When a blood vessel appears like it is not filled
A colour photo will reveal if this is the case or not

Question 28

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

Answer 28

Lack of pigment
-albino
-past infection