What phase is first seen in fluorescein angiography?

In fluorescein angiography, the first phase observed is choroidal flush. This phase occurs when fluorescein dye, injected into a vein, circulates through the bloodstream and reaches the choroidal circulation. The choroid, which is rich in blood vessels and located beneath the retina, rapidly fills with the dye, producing a bright fluorescent signal. This visual phase helps in evaluating the integrity of the choroidal blood vessels and provides baseline information before the dye progresses through retinal vessels.

Choroidal flush is crucial in understanding the overall perfusion of the posterior segment and sets the stage for subsequent phases of the angiography, where details about retinal vascularization and potential pathologies can be identified. The phasing in fluorescein angiography typically progresses from the choroidal flush to the filling of the retinal arteries and veins, thereby establishing a sequence in evaluating vascular conditions of the eye. This foundational knowledge is key for diagnosing various conditions, such as choroidal neovascularization and retinal vascular occlusions.