Dye-free retinal angiography using blood-oxygenation modulation

Abstract

Fluorescence angiography (FA) is widely used for studying and diagnosing abnormalities in the retinal blood circulation, but has associated risks of nausea, skin irritation, and even death. We describe a new non-invasive angiography technique: Blood Oxygenation Modulation Angiography, in which multispectral imaging of a transient perturbation in bloodoxygen saturation, yields angiography sequences similar to FA, including key features such as sequential filling of choroidal and retinal-vessels, which that underpin assessment of circulation health. This is the first non-invasive angiography technique capable of visualizing these circulation features.A These diffuse background characteristics of the "choroidal flush" arise because the light emitted from fluorescein within the choroidal vessels is multiply scattered by the retinal tissue. Further, melanin pigmentation in the retina acts to obscure the dense choroidal vasculature. However, in subjects with low levels of retinal pigmentation, the choroidal blood vessels can be directly observed. [57]