Purpose: To compare the choroidal volume (CV) between emmetropic and highly myopic eyes, and to assess if the presence of myopic fundus abnormalities, myopic traction maculopathy, or choroidal neovascularization affects the CV.
Methods: We retrospectively reviewed imaging studies of 98 eyes of 98 patients who underwent CV measurement on optical coherence tomography. We included 31 emmetropic eyes (Group 1), 36 highly myopic eyes without vitreoretinal or choroidal pathologies (Group 2), 21 highly myopic eyes with traction maculopathy (Group 3), and 10 highly myopic eyes with history of choroidal neovascularization (Group 3). Eyes with chorioretinal atrophy were excluded. Regression analysis was performed to evaluate the correlation between CV and multiple variables.
Results: Choroidal volume was lower in Group 2 than in Group 1 (P < 0.001), and in Groups 3 and 4 than in Group 2 (P < 0.001 and P = 0.002, respectively). Age (P = 0.002), axial length (P < 0.001), sex (P = 0.047), staphyloma (P < 0.001), and myopic group (P = 0.05) were independent predictors for the final CV (R = 0.645). In highly myopic eyes, CV decreased by 0.32 mm for every 10 years and by 0.49 mm per millimeter of axial length.
Conclusion: Choroidal thinning is present in highly myopic eyes compared with emmetropic eyes, and is related to age, axial length, sex, and staphyloma. However, myopic eyes with coexisting myopic traction maculopathy or history of choroidal neovascularization have more severe thinning, likely leading to insufficient metabolic supplementation for the macula.