Fluorescein Angiography.

Fluorescein angiography (FA) or Intravenous Fluorescein Angiography (IVFA) is an imaging modality used to study the circulation of the retina and choroid. It is based on a physical principle where molecules are excited by light within a certain wavelength range, and the emitted wavelength is longer than the excitation light. When this emitted energy occurs in the visible spectrum is called luminescence. The type of excited molecule determines the imaging technique used. In FA, an exogenous molecule is excited, while in autofluorescence, endogenous molecules are excited and detected.