New insight on choroidal vasculature: multimodal morphofunctional approach

maging the choroid in vivo using standard modalities is difficult because of light scattering within overlying tissue, particularly the retinal pigment epithelium (RPE). Although the choriocapillaris is composed of relatively large-diameter capillaries, they are interconnected in a dense arrangement. The flow in the choriocapillaris is fast and because of the prominent fluorescein leakage vascular structure is obscured. Indocyanine green dye shows less leakage than fluorescein, but it still leaks from the choriocapillaris and stains Bruch’s membrane and the choroidal stroma. Optical coherence tomography angiography has high axial resolution, but the lateral resolution is insufficient to visualize the choriocapillaris clearly in the posterior pole. Nevertheless, it can detect choriocapillaris blood flow, producing contrast between the RPE and choriocapillaris. However, because of signal loss, fringe wash-out, and thresholding used in signal processing, the vessels in Sattler’s layer and certainly in Haller’s layer appear dark in normal eyes. Purpose of the lecture is to evaluate various choroidal multimodal imaging findings and to allocate them in the context of different macular diseases.