Correlations between local peripapillary choroidal thickness and axial length, optic disc tilt, and papillo-macular position in young healthy eyes

Optical coherence tomography (OCT) has made it possible for clinicians to measure the peripapillary choroidal thickness (ppCT) noninvasively in various ocular diseases. However, the ocular factors associated with the ppCT have not been conclusively determined. The purpose of this study was to determine the relationship between the local ppCT and the axial length, optic disc tilt, and the angle of the papillo-macular position (PMP) in healthy eyes. This was a prospective, observational cross-sectional study of 119 right eyes of 119 healthy Japanese volunteers. The ppCT was manually measured at eight sectors around the optic disc using the B-scan images of the Topcon 3D OCT RNFL 3.4 mm circle scan. The trajectory of the retinal pigment epithelium in the B-scan image was fitted to a sine curve using ImageJ, and the amplitude of the sine curve was used to determine the degree of the optic disc tilt. The PMP angle was determined in the color fundus photographs. The relationships between the ppCT and the axial length, the optic disc tilt, and PMP angle were determined by Spearman and multiple correlation analyses. The mean age was 25.8 ± 3.9 years and the mean axial length was 25.5 ± 1.4 mm. The ppCT was significantly and negatively associated with the axial length (R = -0.43 to -0.24, P<0.01) and positively associated with the PMP angle (R = 0.28 to 0.37, P<0.01) in all eight circumpapillary sectors. The temporal and infratemporal ppCTs were significantly and negatively associated with the optic disc tilt (R = -0.31, -0.20, P<0.05). The results of multiple regression analyses were similar to that of Spearman correlation analysis. In conclusion, the axial length and PMP angle can affect the ppCT in all circumferential sectors, however the tilt of the optic disc is correlated with only some of the sectors. This should be remembered in interpreting the ppCT.