Investigations

Question 1

What are the phases of the fundus fluorescene angiography

Answer 1

• Choroidal phase (pre - arterial) - 9-15s after dye injections
• Arterial phase - 1s later
• Arteriovenous phase -
• Venous phase - 20-25s, max perifoveal filling
• Late phase
  Fluroscene is absent at approx 10mins

Question 2

Why does the fovea appear dark on FFA

Answer 2

• No blood vessels in FAZ
• High density of xanthophyll at fovea blocking background fluorescence
• Blockage of background fluorescence buy RPE cells which are tallest at fovea and have more melanin and lipofuscin

Question 3

What are the Adverse effects to FA

Answer 3

• Discolouration fo skin and urine
• Pain at area, extravasation
• Nausea/vomiting
• itching/rassh
• Vasovagal
• 1 in 2000 chance of anaphylactic reaction
• 1 in 220,000 chance of death

Question 4

What are the absolute and relative contraindications to FFA

Answer 4

Absolute:
- allergy

Relative:
- renal failure
- pregnancy
- moderate-severe asthma
- significant cardiac disease

Question 5

What is the dose of fluorescein given?

Answer 5

• 5ml of 10% (100mg/ml) solution
• 30mg/kg if oral and pictures taken over 20-60mins

Question 6

Ate what phase doe the cilioretinal artery fill and why?

Answer 6

The choroidal phase - as it is from the choroidal circulation I.e. the long posterior arteries

Question 7

What is the physiological reason for Pooling on FFA and what causes it?

Answer 7

Breakdown of outer-blood-retinal barrier (I.e. RPE tight junctions)

Causes:
- Subretinal space: CSR
- Sub-RPE space: PED

Question 8

What is the physiological reason behind Leakage on FFA?

Answer 8

Breakdown in the inner-retinal barrier

Causes:
- Tight junctions lost/dysfunctional - DR, RVO, CMO, papilloedema
- Absence of endothelial tight junctions: CNV, proliferative DR, tumours, Coats etc

Question 9

Why do is most of the ICG retained in the choriocapillaris?

Answer 9

98% bound to protein (albumin mostly) and choriocapillaris impermeable to large molecules

Question 10

What dose of ICG is used?

Answer 10

25-30mg in 1-2 ml of water

Question 11

What are the Phases of ICG?

Answer 11

Early - 60s
Ealry-mid - 1-3 mins
Late- mid - 3-15mins
Late - 15-45mins

Question 12

Contraindications of ICG

Answer 12

Iodine (or possible shellfish) allergy

Relative CI: liver disease (hepatic excretion)

Question 13

How to tell the difference between FFA and ICG

Answer 13

The disc is always dark on ICG

Question 14

Causes of hyperfluorescence in ICG

Answer 14

• Window
• Leakage (from retinal or choroidal vessels or optic nerve or RPE)
• Abnormal retinal or choroidal vessels e.g. polyps

Question 15

Causes of hypofluorescence in ICG?

Answer 15

• Masking (I.e. blockage): pigment, blood, fibrosis, infiltrate, exudate, serous fluid, PED
• Filling defect: loss of choroidal or retinal circulation

Question 16

ICG findings in CSCR:

Answer 16

• choroidal leakage
• dilated choroidal vessels