Which property of indocyanine green makes it suitable for imaging the choroidal circulation during angiography?
- A It is almost completely protein bound, so it remains largely intravascular within the choriocapillaris ✓
- B It is freely water soluble and leaks rapidly through the choriocapillaris
- C It emits in the visible blue spectrum, which is absorbed by the RPE
- D It stains the RPE cells directly, outlining the choroid
Correct answer: A. It is almost completely protein bound, so it remains largely intravascular within the choriocapillaris
Explanation
Indocyanine green is approximately 98 percent protein bound to albumin, so it does not leak through the fenestrated choriocapillaris as fluorescein does. This keeps the dye intravascular and allows clear delineation of larger choroidal vessels. Its excitation and emission peaks lie in the near infrared range around 805 nm, which penetrates the RPE and pigment better than visible light. This is why ICGA is preferred in polypoidal choroidal vasculopathy and chronic central serous chorioretinopathy.
Reference: Ryan's Retina, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.