Abstract
BackgroundTo investigate the repeatability of superficial retinal vessel density measurements in healthy eyes with long axial length (AL) using optical coherence tomography angiography (OCTA).MethodsThere were 60 eyes of 31 volunteers enrolled in this cross-sectional observational study. All subjects underwent OCTA, AL and refraction test. The enrolled eyes were divided into the long AL group (26 mm ≤ AL < 28 mm) and normal AL group (22 mm ≤ AL < 26 mm). The vessel length density (VLD), perfusion density (PD), and fovea avascular zone (FAZ) of the superficial retinal vessel were evaluated. Repeatability was assessed by intraclass correlation coefficients (ICCs) and Bland-Altman analysis. Pearson’s r correlation was used to analyze the relation of AL and the absolute difference between two measurements.ResultsThe 3 × 3 mm scan pattern showed good repeatability with all ICCs over 0.7. For all parameters of all scan patterns, the ICCs of the normal AL group were distinctly higher than those of the long AL group; this finding was also confirmed by Bland-Altman analysis. The correlation analysis of AL and repeatability of OCTA parameters showed significant negative correlations between the ALs and repeatability of VLD in 6 × 6 mm inner ring (r2 = 0.13, p = 0.01), VLD in 6 × 6 mm outer ring (r2 = 0.09, p = 0.02) and PD in 6 × 6 mm outer ring (r2 = 0.08, p = 0.03).ConclusionsThe AL and the scanned area will both affect the repeatability of superficial retinal vessel density measurements in OCTA.
Highlights
Optical coherence tomography angiography (OCTA) is an advanced imaging technique that allows depth resolved study of retinal microvascular networks
The raw data of vessel length density (VLD), perfusion density (PD) and fovea avascular zone (FAZ) values for 3 × 3 mm and 6 × 6 mm were shown in Additional file 1
For all parameters of all scan patterns, the Intraclass correlation coefficient (ICC) of the normal axial length (AL) group were distinctly higher than those of the long AL group; this finding was confirmed by Bland-Altman analysis
Summary
Optical coherence tomography angiography (OCTA) is an advanced imaging technique that allows depth resolved study of retinal microvascular networks. ZEISS AngioPlex Metrix software provides automatic quantitative analysis of retinal vessels in the superficial layer, including the fovea avascular zone (FAZ), Li et al BMC Ophthalmology (2018) 18:326 vessel length density (VLD) and perfusion density (PD), but the repeatability remains unclear. The FAZ, VLD and PD of the superficial retinal vasculature have been reported to have high repeatability but can be affected by many factors, such as scan order [8]. We intend to explore the correlation between the repeatability of OCTA parameters and AL of healthy young adults for better understanding and interpretation of vascular perfusion in patients with axial myopia. To investigate the repeatability of superficial retinal vessel density measurements in healthy eyes with long axial length (AL) using optical coherence tomography angiography (OCTA)
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