OCT Angiography Flow Index and Projection Artifacts in Outer Retina

Abstract

Introduction: Ocular vasculature investigation has always been difficult. Many devices have been invented to measure the hemodynamics of the eye but none of them completely satisfied the requirements because of specific limitations. With optical coherence tomography-angiography (OCTA) it is now possible to assess parameters of ocular hemodynamics non-invasively and quantitatively. Vessel density or density (%) and flow index or flow area (mm2) are quantitative parameters with proven importance in inner retinal diseases like glaucoma. The purpose of this work is to demonstrate quantitative flow area changes in external avascular retina as a result of diseases affect inner retinal layers and vessel density. Material and methods: Our observations are summarized via presentation of several case controls as a representative sample of the total number of participants. We investigated controls and patients with proven inner retinal disease (glaucoma and multiple sclerosis – MS). Non-invasive angio-OCT imaging technique was applied (AngioVue, OptoVue) and Flow Area values were measured in posterior pole around macula in circle area with maximum radius of 1.50 mm. Results: The investigation of Flow area parameter in external retina shows decreasing of the values in inner retinal diseases like glaucoma or neuritis optica associated with MS. It is best demonstrated when asymmetrical process is observed between two eyes. Conclusion: Flow area values vary over a large range in healthy people and a lot of factors may influence the results. Quantitative analysis of Flow area in external retina is a combination between artifacts (projection and dark areas) and real for external retina Flow area values. Flow area changes are indirect reflection of an inner retinal state.