Guidelines for Imaging the Choriocapillaris Using OCT Angiography

PURPOSE: To provide guidance on how to appropriately quantitate various choriocapillaris (CC) parameters with optical coherence tomography angiography (OCTA). DESIGN: Evidence-based perspective. METHODS: Review of literature and experience of authors. RESULTS: Accurate and reliable quantification of CC using OCTA requires that CC can be visualized and that the measurements of various CC parameters are validated. For accurate visualization, the selected CC slab must be physiologically sound, must produce images consistent with histology, and must yield qualitatively similar images when viewing repeats of the same scan or scans of different sizes. For accurate quantification, the measured intercapillary distances (ICDs) should be consistent with known measurements using histology and adaptive optics and/or OCTA, the selected CC parameters must be physiologically and physically meaningful based on the resolution of the instrument and the density of the scans, the selected algorithm for CC binarization must be appropriate and generate meaningful results, and the CC measurements calculated from multiple scans of the same and different sizes should be quantitatively similar. If the Phansalkar local thresholding method is used, then its parameters must be optimized for CC based on the OCTA instrument and scan patterns used. It is recommended that the window radius used in the Phansalkar method should be related to the expected average ICD in normal eyes. CONCLUSIONS: Quantitative analysis of CC using commercially available OCTA instruments is complicated, and researchers need to tailor their strategies based on the instrument, scan patterns, anatomy, and thresholding strategies to achieve accurate and reliable measurements. (Am J Ophthalmol 2021;222: 92-101.

Automated summary

Accurate visualization and quantification of choriocapillaris (CC) parameters are essential for OCTA analysis. Physiologically sound CC slabs and appropriate algorithms are crucial for reliable measurements. Researchers should tailor their strategies based on instrument specifications and scan patterns to achieve accurate results.