9.9  Fundus Angiography - Indocyanine Green

Indocyanine Green (ICG) Angiography, often used to complement Fundus Fluorescein Angiography (FFA), is a procedure used to acquire images of the choroidal vasculature. Indocyanine Green is a water-soluble dye which is almost entirely protein-bound (98%) which limits its diffusion out of the choroidal vasculature. It fluoresces in infrared light (790 – 805 nm) which has the ability to penetrate the retinal pigmented epithelium (RPE) and blood and allows for visualisation of the choroidal circulation. Following intravenous injection of ICG, the dye remains in the retinal and choroidal vessels and the fluorescence can be detected by fundus cameras or confocal scanning laser ophthalmoscopes. Images are captured at 1-minute intervals up until 5 minutes and then at 5 minute intervals up until 20 minutes.

Mild side effects of ICG include nausea, vomiting and pruritus. It should not be used in patients with an iodine allergy and in patents with liver disease or uraemia. ICG is classified as a Category C drug in pregnant women (have caused or may be suspected of causing, harmful effects on the human foetus or neonate without causing malformations - these effects may be reversible) and should be avoided.

Phases of ICG-Angiography:

i. Early Phase (First 1-minute Post Injection)
  • Choroidal arteries shown
ii. Early Mid-phase (1 - 3 Minutes)
  • Choroidal veins and retinal vessels seen clearly
iii. Late Mid-phase (3 - 15 Minutes)
  • Structures fluorescing: Choroidal vessels fading but retinal vessels are still visible
iv. Late Phase (15 - 45 Minutes)
  • Structures fluorescing: Gradual fading of diffuse hyperfluoresence

Normal Examples

Figure 9.9.1 Normal ICG Angiogram 1 Minute 15 Seconds Post Injection (Early Mid-Phase)

Figure 9.9.1
Normal ICG Angiogram 1 Minute 15 Seconds Post Injection (Early Mid-Phase)

Figure 9.9.2 Normal ICG Angiogram 5 Minutes Post Injection (Late Mid-Phase)

Figure 9.9.2
Normal ICG Angiogram 5 Minutes Post Injection (Late Mid-Phase)

ICG has the advantage over fluorescein of being able to fluoresce better through pigment and haemorrhage. It is particularly useful in the following conditions:

  • Polypoidal Choroidal Vasculopathy (PCV) – hyperfluorescent polyps
  • Central Serous Chorioretinopathy (CSR)- mid-phase hyperfluorescence
  • Choroidal inflammatory diseases such as birdshot choroidoretinopathy and APMPPE
  • Choroidal Tumours such as choroidal haemangioma

Contents

Figure 9.9.3 Acute Posteior Multifocal Placoid Pigment Epitheliopathy (APMPPE)

Figure 9.9.3
Acute Posteior Multifocal Placoid Pigment Epitheliopathy (APMPPE)

Figure 9.9.4 Acute Posterior Multifocal Placoid Pigment Epitheliopathy (APMPPE) (Late Phase)

Figure 9.9.4
Acute Posterior Multifocal Placoid Pigment Epitheliopathy (APMPPE) (Late Phase)

Figure 9.9.5 Choroidal Haemangioma

Figure 9.9.5
Choroidal Haemangioma

Figure 9.9.6 Polypoidal Choroidal Vasculopathy (PCV)

Figure 9.9.6
Polypoidal Choroidal Vasculopathy (PCV)

The hyperfluorescent spot represents a polyp which is a classical finding in PCV.

Figure 9.9.7 Ruptured Macroaneurysm
The hyperfluorescent spot represents a macroaneurysm with an adjacent area of retinal haemorrhage.

Figure 9.9.7
Ruptured Macroaneurysm

The hyperfluorescent spot represents a macroaneurysm with an adjacent area of retinal haemorrhage.

          

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