### Materials and Methods

*p*< 5% level, abnormal glaucoma hemifield test result, or any other pattern of loss consistent with ocular disease) in either eye; (3) history of ocular surgery; (4) best-corrected visual acuity worse than 20 / 32 on Early Treatment of Diabetic Retinopathy Study scale; (5) evidence of vitreoretinal disease; (6) evidence of optic nerve or RNFL abnormality; and (7) history of diabetes or other systemic disease.

*t*=

*p*·

*q*·

*s*, where "

*t*" is the actual size, "

*s*" is the size measured on the fundus photograph, "

*p*" is the magnification factor related to the camera, and "

*q*" is the magnification factor related to the eye [18]. The magnification factor related to the fundus camera, "

*p*," can be expressed as a constant of 3.382 in the telecentric system of Stratus a nd Cirrus OCT [19]. The ocular magnification factor related to the eye, "

*q*," was calculated by the modified axial length method proposed by Bennett et al. [20] [

*q*= 0.01306 · {axial length (mm) - 1.82}].

*r*, radius of scan circle = 1.73 mm;

*r*', magnified radius of scan circle).

*p*-values less than 0.01 were considered statistically significant.

### Results

^{2}, the r im area was 1.308 ± 0.264 mm

^{2}, and the average C/D ratio was 0.539 ± 0.149. A correlation analysis of the axial length with disc area, rim area, cup area, C/D ratio, and peripapillary RNFL thickness showed negative results. The distance from the disc margin to the scan circle (1.73-disc radius) showed positive correlation with axial length. A partial correlation analysis of the same variables, which controlled for the spherical equivalent, showed negative correlation with axial length, whereas the distance from the disc margin to the scan circle showed a positive correlation. A correlation analysis of the spherical equivalent with the disc area, rim area, cup area, C/D ratio, and RNFL thickness showed positive correlations, while that of the spherical equivalent with the distance from the disc margin to the scan circle showed a negative correlation. A partial correlation analysis that controlled for the axial length also revealed positive correlations of the spherical equivalent with the ONH parameters and peripapillary RNFL thickness and a negative correlation with the distance from the disc margin to the scan circle (Table 2). The adjusted values of the disc area, rim a rea, radius of the scan c ircle, a nd a verage RNFL thickness all showed significant positive correlation with the axial length, regardless of the spherical equivalent. Adjusted cup area correlated negatively with the axial length, but this was without statistical significance. All of the adjusted parameters showed negative correlation with the spherical equivalent (Table 3). The same relationships were observed in the results of a linear regression analysis. Specifically, as the axial length increased, the disc area, disc radius, and average RNFL thickness decreased, whereas the distance from the disc margin to the scan circle (of 1.73-mm radius) increased significantly. Also, as the spherical equivalent increased, the disc area, disc radius, and average RNFL thickness increased, and the distance from the disc margin to the scan circle decreased significantly. After adjustment for the ocular magnification effect, as the axial length increased, the disc area, disc radius, and average RNFL thickness decreased, and the distance from the disc margin to the scan circle increased significantly; as the spherical equivalent increased, the disc area, disc radius, average RNFL thickness, and the distance from the disc margin to the scan circle decreased (Figs. 1A-1F and 2A-2F). The measured RNFL thickness without the adjusted ocular magnification effect was analyzed using correlation and simple linear regression analyses to investigate the relationship between disc size and scan circle radius. It was found that the measured RNFL thickness was larger in the eyes with a longer disc radius both before and after adjustment for the ocular magnification effect. In contrast, with the adjusted scan circle, the measured RNFL thickness was smaller in the eyes with a longer distance from the disc margin to the scan circle. Finally, the eyes with the longer axial length and larger myopic refractive error showed smaller peripapillary RNFL thickness as measured by spectral-domain OCT (Table 4).