Purpose: Axial myopia is associated with elongation of the posterior ocular segment. The authors measured posterior fundus landmarks and assessed their associations with axial length.
Methods: Using fundus photographs, the authors measured the vertical distance between the temporal superior and temporal inferior arterial arcade (VDA) and the angle kappa between the temporal arterial arcades among other morphometric variables.
Results: The study included 456 eyes with a mean age of 61.2 ± 14.2 years (range: 13-88 years) and mean axial length of 29.4 ± 2.1 mm (range: 23.2-35.3 mm). Mean angle kappa was 91.3 ± 17.2° (range: 39-161°), and mean VDA was 7.93 ± 1.71 mm (range: 2.72-12.85 mm). In multivariate regression analysis, wider angle kappa was associated (regression coefficient r: 0.47) with shorter axial length (P = 0.002; beta: -0.17; B: -1.37; 95% confidence interval [CI]:-2.23 to -0.51), longer VDA (P < 0.001; beta: 0.27; B: 2.70; 95% CI: 1.85-3.54), shorter disk-foveola distance (P < 0.001; beta: -0.22; B: -4.76; 95% CI: -7.05 to -2.46), shorter vertical optic disk diameter (P = 0.002; beta: -0.14; B: -6.83; 95% CI: -11.1 to -2.56), lower number of any chorioretinal lesions (P = 0.007; beta: -0.13; B: -2.11; 95% CI: -3.63 to -0.58), and longer maximal vertical chorioretinal lesion diameter (P = 0.05; beta: 0.09; B: 0.92; 95% CI: -0.02 to 1.86). A longer VDA was associated (r: 0.31) with longer axial length (P < 0.001; beta: 0.22; B: 0.18; 95% CI: 0.10-0.25), wider angle kappa (P < 0.001; beta: 0.28; B: 0.03; 95% CI: 0.02-0.04) and higher number of chorioretinal lesions (P = 0.03; beta: 0.10; B: 0.16; 95% CI: 0.02-0.31). If eyes with chorioretinal lesions were excluded, the association between longer VDA and longer axial length was no longer statistically significant (P > 0.10).
Conclusion: Axial elongation was correlated with decreasing angle kappa, caused by an elongation of the disk-foveola distance because of an enlargement of the gamma zone, whereas VDA remained constant. By contrast, horizontal length of macular Bruch membrane and vertical length of macular Bruch membrane were independent of axial elongation. Axial elongation did not lead to lengthening of Bruch membrane in the macular region in eyes without macular chorioretinal lesions.