Which phase is first seen (recorded) in fluorescein angiography?

In fluorescein angiography, the first phase that is recorded after injecting fluorescein dye into the bloodstream is known as the choroidal flush. This phase occurs very quickly after the dye enters the circulatory system and allows for the visualization of the choroidal circulation, as the dye rapidly fills the choroidal vasculature.

The choroidal flush is characterized by a homogeneous pattern of fluorescence due to the high blood flow in the choroid, primarily supplying the outer layers of the retina. This early phase is essential as it provides vital information about the integrity of the choroidal blood supply and helps in assessing conditions that may affect the choroid or outer retina.

Following the choroidal flush, the arterial phase is seen, where the dye begins to fill the retinal arteries, ultimately progressing to the venous phase as the dye moves into the venous system. The late phase, characterized by the pooling of dye in areas of abnormal leakage or staining, occurs last and showcases different pathological features. Understanding the sequence of these phases enhances the interpretation of the angiographic results.