Retinal Thickness and Axial Length

PURPOSE. To examine the relationships between axial length and foveal and peripheral retinal thickness. METHODS. Using optical coherence tomography, foveal retinal thickness was measured in participants of the population-based Beijing Eye Study without optic nerve or macula diseases. Inner and outer nuclear layer thickness as surrogate for retinal thickness was assessed in the fundus periphery in human globes enucleated due to malignant uveal melanoma or painful glaucoma. RESULTS. The study included 1117 individuals with a mean age of 64.2 +/- 9.7 years (range: 50-93 years) and mean axial length of 23.4 +/- 1.04 mm (range: 20.29-28.68 mm). In multivariate analysis, thicker central foveal thickness was associated with male sex (P < 0.001; standardized regression coefficient beta: -0.13; nonstandardized regression coefficient B: -5.84; 95% confidence interval (CI): -8.56, -3.13); urban region of habitation (P = 0.02; beta: 0.07; B: 3.56; 95% CI: 0.55, 6.57); thinner lens thickness (P = 0.01; beta: -0.08; B: -5.11; 95% CI: -9.01, -1.21); thinner subfoveal choroidal thickness (P = 0.04; beta: -0.07; B: 0.01; 95% CI: 0.03, 0.001); and longer axial length (P < 0.001; beta: 0.18; B: 3.79; 95% CI: 2.41, 5.17). In the same multivariate model, superior, inferior, and temporal foveal thickness was not significantly associated with axial length (P = 0.26, P = 0.19, P = 0.08, respectively), while thicker nasal foveal thickness was associated with longer axial length (P = 0.009; beta: 0.09; B: 1.50; 95% CI: 0.37, 2.62). In the histomorphometric part of the study including 32 eyes (sagittal diameter: 27.0 +/- 4.2 mm; range: 22-37 mm), mean thickness of the inner and outer nuclear layers at the equator and at the midpoint equator/posterior pole decreased with longer axial length (P = 0.004; beta: -0.48; and P = 0.02; beta: -0.44, respectively). CONCLUSIONS. Myopic axial globe elongation was associated with retinal thinning in the equatorial and pre-equatorial region, while foveal retinal thickness was mostly unaffected by axial length. It suggests that axial elongation takes place predominantly in the equatorial and pre-equatorial region of the eye.