Purpose: We aimed to compare best corrected visual acuity, macular pigment optical density and macular thickness in patients with breast cancer, who received oral adjuvant hormone therapy. Materials and Methods: We enrolled consecutive eligible patients with breast cancer who were receiving regular medical tamoxifen treatment. The participants were divided into two groups as cases and controls. Best-corrected visual acuity and retinal thickness were examined. Macular pigment optical density was measured by fundus reflectometry using the one-wavelength reflection method. The output parameters included max optical density, mean optical density, volume and area of the right eye. Results: A total of 104 eyes, cases (n: 50) and controls (n: 54) were included in the study. Mean age in cases was 49.95 +/- 9.2 years and 50.21 +/- 9.3 years in controls (p = .151). The mean foveal optical density and the maximum optical density differed between cases (0.13 +/- 0.03 density units (DU)/0.35 +/- 0.07 DU) and controls (0.18 +/- 0.04 DU/0.41 +/- 0.06 DU) (p = .002/p = .009). Macular pigment optical density volume was 8102.84 +/- 2412.67 in cases versus 8280.18 +/- 2904.56 in controls (p = .034), and mean MPOD area was 59567.79 +/- 11538.06 in cases versus 61748.14 +/- 10591.19 in controls (p = .023). The best corrected visual acuity and retinal thickness were similar in both groups (p > .05). Conclusions: Patients in care of oral tamoxifen therapy were found to have significantly reduced macular pigment optical density. In addition, higher drug use duration correlated significantly with reduced macular pigment optical density, suggesting that the poor long-term effects may play a role in macular pigment absorption and incorporation in the retinal tissue.