The Correlation of Peripapillary and Juxtapapillary Choroidal Thickness in Healthy Subjects

PURPOSE: To evaluate the correlation between the two methods of measuring the choroidal thickness around the optic nerve head (ONH). METHODS: We conducted a cross-sectional study. Sixty-two eyes of 62 healthy subjects were included. Using spectral domain optical coherence tomography, a peripapillary circle scan (diameter of 3.5 mm) and 24 radial B-scan images centered on the Bruch’s membrane opening (BMO) were obtained. Peripapillary choroidal thickness (PPCT) and juxtapapillary choroidal thickness (JPCT) were measured using circle and radial B-scan images, respectively. Correlation and agreements between values measured by two methods were analyzed. Factors associated with PPCT and JPCT, and the difference between the values measured by the two methods were evaluated. RESULTS: A total of 62 eyes of 62 healthy subjects were enrolled. Average PPCT and JPCT were 165.2 ± 50.1 and 139.7 ± 39.2 μm, respectively. The linear regression analysis showed a strong correlation between both measurements (PPCT vs. JPCT, r(2) = 0.900, p < 0.001). PPCT and JPCT measurements showed good agreement in global and all six sectors (intraclass correlation coefficients >0.900). Bland-Altman plot showed good agreement between the two methods with a systematic deviation of 17.9 μm and a 95% limits of agreement (±1.96 standard deviation) of −9.6 to 60.5. In multivariate regression analysis, BMO area (β = −11.87, p = 0.002) was the only factor significantly correlated with the difference between PPCT and JPCT, which showed a negative correlation. The difference between PPCT and JPCT measurements (PPCT - JPCT) showed a divergent tendency with decreasing BMO area size. CONCLUSIONS: The two measures of choroidal thickness around the ONH were well correlated. However, the peripapillary choroid was generally thicker than the juxtapapillary choroid, especially in eyes with small BMO area.