Macular diseases cause vision loss, as the macula is the functional center for vision. In this study we assessed optical quality in eyes with macular diseases and evaluated the effectiveness of the Optical Quality Analysis System (OQAS) to detect macular diseases. We analyzed 88 eyes of 88 patients with macular diseases (51 men and 37 women; mean age: 65.24 ± 12.96 years) and 43 eyes of 43 control subjects (11 men and 32 women; mean age: 54.70 ± 15.03 years). The macular diseases included age-related macular disease (n = 62), diabetic macular edema (n = 19), and retinal vein occlusion (n = 7). We measured the objective scattering index (OSI), modulation transfer function (MTF), Strehl ratio, and predicted visual acuities (PVAs) at 100, 20, and 10% contrast levels in both groups using OQAS. We measured the retinal thickness in the macular disease group on optical coherence tomography. The macular disease and control groups significantly differed in OSI, MTF, Strehl ratio, and PVAs at 20 and 10% contrast levels (p < 0.05). In the macular disease group, retinal thickness correlated with OSI (r = 0.370, p < 0.001) and MTF (r = −0.264, p = 0.014). In conclusion, optical quality was worse in the patients with macular diseases compared to the control subjects, and retinal thickness affected optical quality. Therefore, the distortion of macular shape may contribute to vision disturbance in patients with macular diseases.