Normal Fundus Fluorescein Angiography

Abstract

Fundus fluorescein angiography (FFA) is an important imaging modality for the diagnosis and management of uveitis. Fluorescein is a small molecule which when stimulated by blue light at a wavelength of 465–490 nm emits a yellowish-green light between 520 and 530 nm. FFA requires the use of a dedicated fundus camera equipped with excitation and barrier filters. Normal retinal pigment epithelium and retinal vascular endothelium are impermeable to fluorescein. Several complications may occur during FFA. Nausea is the most common reaction seen in 3–5% of patients. Life-threatening complications such as anaphylaxis, cardiac arrest, and bronchospasm are possible but extremely rare. After the intravenous injection of the dye, it appears in the optic nerve and choroid within 8–12 s. The choroidal phase is seen as a patchy and mottled hyperfluorescence. Fluorescein appears in the arteries 1–3 s later. Complete filling of the arteries and capillaries and the first evidence of laminar flow in the veins characterize the arteriovenous phase. The venous phase corresponds to the complete filling of retinal veins by the dye. During the recirculation phase, beginning roughly 1 min after the injection, there is a decreasing fluorescence within the retinal vessels. During FFA, choroidal fluorescence is relatively blocked by the retinal pigment epithelium screen.