Pupil vignetting artifact on optical coherence tomography angiography

Abstract

Purpose: To discuss the features of an artifact on optical coherence tomography angiography (OCTA), termed “pupil vignetting artifact,” and describe how it may masquerade as true chorioretinal pathology. Design: This was a retrospective, observational case series. Methods: The authors studied 12 eyes at a vitreoretinal clinic in Eastern India, reviewing a dark shadow such as an artifact on OCTA images. Results: In all 12 eyes, there was an appearance of a dark shadow on OCTA imaging, located at the macula, superior, superotemporal, or superonasal to the fovea, which did not correspond to any ischemic area responsible for flow-void or any media opacity casting a posterior shadow. It was believed to be an artifact caused by the vignetting effect of the pupil as the incident OCT beam clips the iris during OCTA scanning, and therefore reduces the amount of total light incident on the retina. The variability in the size, shape, and location of the artifact is contributed by a few factors such as variable angle of incident light on the pupil, pupillary dynamics, and curvature of the retinal surface. Conclusion: Pupil vignetting artifact is a unique undescribed phenomenon appearing at the macula on OCTA imaging that can masquerade as numerous true chorioretinal pathologies. This article aims to describe this artifact to avoid misinterpretation and further confusion in real-life clinical practice.

Keywords

• flow-void
• low oct-signal artifact
• optical coherence tomography
• optical coherence tomography angiography
• vignetting artifact