Reliability of Optical Coherence Tomography Angiography Retinal Blood Flow Analyses.

Purpose: Investigate the association between the optical coherence tomography angiography (OCTA) metrics derived from different analysis programs to understand the comparability of studies using these different approaches. Methods: Secondary analysis of a prospective observational study (March 2018-September 2021). Forty-four right eyes and 42 left eyes from 44 patients were included. Patients were either undergoing upper gastrointestinal surgery with a critical care stay planned or were already in the critical care unit with sepsis. OCTA scans were obtained in an ophthalmology department or critical care setting. Fourteen OCTA metrics were compared within and between the programs, and agreement was measured by Pearson's R coefficient and intraclass correlation coefficient. Results: Correlation was highest between all Heidelberg metrics and Fractalyse (all >0.84), and lowest between Matlab skeletonized or foveal avascular zone metrics and all other measures (e.g., skeletal fractal dimension and vessel density at -0.02). Agreement between eyes was moderate to excellent in all metrics (0.60-0.90). Conclusions: The significant variability between metrics and programs used for OCTA analysis demonstrates that they are not interchangeable and supports a recommendation for perfusion density metrics to be reported as standard. Translational Relevance: Agreement between different OCTA analyses is variable and not interchangeable. The high agreement between non-skeletonized vessel density metrics suggests that these should be routinely reported.