Blue visual field defects occur when the tissues in the eye that control the color blue become abnormal. Visual field defects are a common symptom of many neurological disorders, and damage to different parts of the visual pathway and different diseases can lead to different visual field defects. So, how do older adults detect blue visual field defects early? The following is a diagnostic method: Self-test method is to hold out a hand, gently cover a glance, at this time look at a target in front of you, carefully observe whether there is a part of the range you see can not be seen, can not see, or the area seen is significantly reduced. A normal person’s field of vision is approximately 56 degrees above, 65 degrees to the nasal side, 74 degrees below and 91 degrees to the lateral side. If any of these conditions exist, it is a sign that an older person may have a visual field defect. The above examination is only a rough self-test, if elderly people feel that they have visual field defects, they can go to the hospital for an accurate visual field examination. The doctor can use the visual field examination results to analyze the cause of the disease and the severity of the disease.