Vessel/perfusion density in two optical coherence tomography angiography protocols. Interchangeable?

Introduction: Different optical coherence tomography angiography (OCTA) scanning protocols evaluate the macula. Objective: To compare the determination coefficients (R2) between vessel and perfusion densities of two OCTA scanning protocols, to learn whether their metrics could be interchanged. Method: Non-experimental, comparative, prospective, observational, cross-sectional study, between two OCTA scanning protocols (Angioplex, Zeiss) in healthy subjects. We found the R2 between central, inner, and full densities (3 x 3 mm protocol), and between central, inner, outer and full densities (6 x 6 mm protocol), both for vessel and perfusion densities. Results: 78 eyes, median age 23 years. There were high R2 between inner and full densities in the 3 x 3 mm protocol (0.96), between outer and full densities in the 6 x 6 mm protocol (0.96) and between central vessel and perfusion densities (>= 0.96); R2 between central vessel and perfusion densities of different protocols (<= 0.71). Conclusions: Vessel and perfusion densities have high determination coefficients within a scanning protocol, but not between protocols, because each preferentially measures different macular areas. The metrics of different protocols should not be interchanged for follow-up.