Pupillary distance refers to the distance between the centers of the two pupils when the human eye is orthogonal and parallel to the visual axis. A pair of glasses consists of two optical lenses, the distance between the optical center of the two lenses should be consistent with the human pupillary distance, the human eye will feel comfortable, when there is a large deviation will be obvious discomfort, generally through the clinical performance with the pupillary distance measurement, can determine whether the correct pupillary distance of glasses. I, determine the glasses pupil distance incorrect method 1, according to clinical performance judgment: glasses pupil distance is incorrect, will affect the focus of vision, easy to double vision, blurred vision, and even nausea, dizziness, eye swelling, vomiting and other discomfort; 2, according to professional testing judgment: go to a professional dispensing center, use the pupil distance meter to measure, by measuring the distance between the pupil of both eyes and the lens optical center distance to judge. Second, the glasses pupil distance is not right cause glasses pupil distance is not right, mostly with the lens and frame specifications are not coordinated. But in the optometry, the wrong optometry or inaccurate measurement of the pupil distance, will also cause the glasses pupil distance is not right. In the case of optometry, it is recommended to go to a regular prescription center to accurately measure the pupil distance and further understand the other problems of the eyes. The pupil distance of eyeglasses is not correct, which not only brings discomfort to the patient, but also affects the effect of vision correction, which can also lead to further vision loss and increase myopia. Therefore, you should promptly go to a professional prescription center to re-measure the pupil distance to see if the lens and frame specifications are not coordinated, and choose a frame that is consistent with the geometric center distance and pupil distance.