If one eye is bright and the other eye suddenly appears dark, it is considered a problem with the retina. When there is a problem in this area, the first reaction will be blurred and darkened vision, and it may be accompanied by corresponding distortion of vision or change in size of vision. Therefore, when an eye suddenly appears dark, observe whether there is any corresponding color, size and shape change, if there is any of these changes, it means that there is a problem in the macula. If there is any of these changes, it means that there is a problem in the macula. Through this examination, we can make a clear diagnosis of most macular diseases, such as macular edema, macular anterior membrane or hemorrhage, and after a clear diagnosis, we can carry out symptomatic treatment according to the cause.