Imaging of iris vasculature: current limitations and future perspective

Fluorescein and indocyanine green angiography have been the traditional ways to image the vasculature of the iris in the last few decades. Because of the invasive nature of these procedures, they are performed in rare situations, and thus, our understanding about iris vasculature is very limited. Optical coherence tomography angiography (OCTA) is a noninvasive imaging method that enables the detailed visualization of the retinal and choroidal vascular networks. More recently, it has been also used for the examination of the iris vasculature in healthy and disease eyes. However, there is a lack of uniformity in the image acquisition protocols and interpretations in both healthy and pathological conditions. Artifacts of iris OCTA include shadowing, motion, segmentations errors, mirror effects. OCTA devices have an eye-tracking system designed for the posterior segment and the applications of these systems on the anterior segment can determine motion lines, vessel duplication, and vessel discontinuity. OCTA of the iris should always be performed under ambient room lighting to create miosis and reduce iris vasculature changes during the examination. In the near future, eye-tracking systems specifically designed for the iris vessels could permit the follow-up function, and the development of new OCTA metrics could reveal interesting applications of this new imaging technique.