Fluorescein Angiography

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Fluorescein

  • Binds 80% to albumin and other serum proteins
  • 90% excreted by kidneys (remainder via liver) within 24 – 36 hours

Phases

  • Fluorescein enters the choroidal circulation through short posterior ciliary arteries, approximately 10 -15 seconds after injection (Arm-Retina time should be <20 seconds); choroidal capillary filling phase usually completes during arteriovenous or early venous phase
  • Central artery filling occurs about 1-2 seconds after choroidal filling
  • Arteriovenous (AV) phase occurs 1-2 seconds after arterial phase
  • Venous filling takes about 10 – 12 seconds

Side Effects

  • Skin and conjunctival discoloration for up to 8 – 12 hours post injection
  • Nausea (3 – 15%)
  • Vomiting (5%)
  • Pruritus (5%)
  • Anaphylactic reaction 1 in 100,000
  • Death 1 in 220,000

Findings

  • Hyperfluorescence:
    • Leakage: in fenestrated choriocapillaris, iris vessels
    • Staining: in structures like collagen
    • Pooling: in fluid accumulations
    • Window defects: in RPE defects
  • Hypofluorescence:
    • Blocking phenomenon: due to opacities reducing fluorescence, e.g., RPE, blood, xanthophyll
    • Filling defect: in ischemia
  • CAUTION: Fluorescein passes the Bruch’s membrane but not the RPE or retinal capillaries
  • Autofluorescence
    • Visible before fluorescein administration, e.g., in optic disc drusen, in astrocytic hamartomas, in large lipofuscin deposits

Sources