Patients with oval blue shadow in the middle of one eye may be caused by central plasma choroidal retinopathy, fundus macular degeneration and iris nevus. 1. Centralized plasma choroidal retinopathy: affected by various factors such as mental illness and bad life habits, it may lead to centralized plasma choroidal retinopathy, which will affect the retina and make the patient have symptoms such as change of vision and oval blue shadow in the middle of one eye. 2. Macular degeneration of the fundus: with age and inflammation and other factors stimulation, may lead to patients with macular degeneration of the fundus, so that patients appear vision deformation and oval blue shadow in the center of one eye and other discomfort symptoms. 3. Iris nevus: Iris nevus may be formed congenitally, and its specific cause is not yet clear, after suffering from this disease, it will lead to iris color variation, and when the size of nevus is large, it can block the patient’s field of vision. It is recommended that patients with oval blue shadow in the center of one eye should consult a doctor in time to evaluate their condition and follow the doctor’s instructions for treatment.