Reliability of Vessel Density Measurements in the Peripapillary Retina and Correlation with Retinal Nerve Fiber Layer Thickness in Healthy Subjects Using Optical Coherence Tomography Angiography

Purpose: To evaluate the reliability of vessel density measurements in the peripapillary retina using optical coherence tomography angiography (OCT-A) and to analyze the correlation with retinal nerve fiber layer (RNFL) thickness in healthy subjects. Method: Thirty-five healthy volunteers were recruited in the study. The optic disc region was scanned three times with spectral-domain OCT (SD-OCT) and split-spectrum amplitude decorrelation angiography by two skilled examiners. Vessel density of the peripapillary retina was automatically calculated by the software RTVue-XR (version 2015.1.1.98). The RNFL thickness on the optic nerve head was measured by SD-OCT. The coefficient of variation (CV), coefficient of repeatability, and intraclass correlation coefficients (ICC) were calculated for intraobserver repeatability. The Bland-Altman analysis was used to determine interobserver reproducibility. Correlations between peripapillary retinal vessel density and RNFL thickness were analyzed using a multivariable linear regression. Results: The mean age of the volunteers was 47.0 +/- 29.7 years. The intraobserver repeatability in different sectors of the peripapillary retina was good with a high coefficient of repeatability, low CV (< 0.2%), and high ICC (0.847-0.952). The interobserver reproducibility was also good in different sectors, but should be interpreted with caution due to the difference bias caused by different observers in some quadrants. There was a significant positive correlation between vessel density and RNFL thickness; optic disc rim area and disc area were negatively related to vessel density (p = 0.008 and p = 0.001, respectively). Conclusion: Vessel density measurements showed good repeatability and reproducibility by OCT-A in the peripapillary retina, the vessel density was positively related to RNFL thickness and negatively related to optic disc area and rim area.