What phase is first recorded in fluorescein angiography?

In fluorescein angiography, the first recorded phase is the choroidal flush. During this initial phase, a rapid influx of fluorescein dye into the choroidal circulation occurs, which is characterized by the filling of the large choroidal vessels. This results in a bright appearance of the choroid on the angiographic images. It happens quickly after the injection of the dye, typically within seconds, providing vital information about the blood supply to the outer retina.

Understanding this phase is crucial for interpreting the subsequent phases of the procedure, such as arterial uptake, venous filling, and retinal perfusion, each of which provides insights into the vascular status and health of the retina. However, none of these phases precedes the choroidal flush; instead, they occur in a sequential manner after it, making the choroidal flush the cornerstone phase for analyzing the vascular dynamics captured during fluorescein angiography.