Pupil distance difference of 2mm may have an effect. Generally, when dispensing eyeglasses, the error of pupil distance of one eye should not be more than 0.5mm, and that of both eyes should not be more than 1mm, so the difference of pupil distance of 2mm may have an effect. For eyes with refractive error, when using glasses for optical correction, it is necessary to match the position of the optical center of the spectacle lens with the position of the pupil so as to achieve the best optical compensation effect, so the pupillary distance is an important parameter in the prescription of glasses, and a difference of 2mm in the pupillary distance may have an effect. If the error of pupillary distance is large when dispensing eyeglasses, there will be symptoms such as blurring of wearing glasses, eye discomfort and other symptoms after wearing eyeglasses, and in serious cases, it will also affect the vision of eyes, and there will be symptoms such as visual fatigue, dizziness and eye distension, and loss of visual acuity. When the difference between the pupil distance is 2mm, it is recommended to re-measure the pupil distance and fit the glasses, so as not to affect the vision of the eyes.