The Definition, Rationale, and Effects of Thresholding in OCT Angiography.

Purpose: To examine the definition, rationale, and effects of thresholding in OCT angiography (OCTA).
Design: A theoretical description of OCTA thresholding in combination with qualitative and quantitative analysis of the effects of OCTA thresholding in eyes from a retrospective case series.
Participants: Four eyes were qualitatively examined: 1 from a 27-year-old control, 1 from a 78-year-old exudative age-related macular degeneration (AMD) patient, 1 from a 58-year-old myopic patient, and 1 from a 77-year-old nonexudative AMD patient with geographic atrophy (GA). One eye from a 75-year-old nonexudative AMD patient with GA was quantitatively analyzed.
Main Outcome Measures: A theoretical thresholding model and a qualitative and quantitative description of the dependency of OCTA on thresholding level.
Results: Due to the presence of system noise, OCTA thresholding is a necessary step in forming OCTA images; however, thresholding can complicate the relationship between blood flow and OCTA signal.
Conclusions: Thresholding in OCTA can cause significant artifacts, which should be considered when interpreting and quantifying OCTA images.
Competing Interests: Conflicts of Interest: J.S.D.: Consultant and research support — Carl Zeiss Meditec, OptoVue, and Topcon Medical Systems Inc; stock — Hemera Biosciences Inc, EyeNetra, and Ophthotech Corp. N.K.W.: Consultant — Iconic Therapeutics; speaker’s bureau —ThromboGenics; research support — Carl Zeiss Meditec, Inc. J.G.F.: Royalties — intellectual property owned by the Massachusetts Institute of Technology and licensed to Carl Zeiss Meditec Inc, Optovue Inc; stock options — Optovue Inc. There are no conflicting relationships for any other author.