If the pupillary distance is the distance between the pupils of both eyes, it should refer to the pupillary distance, which varies with the distance between the eyes of the face.

The pupillary distance of children is small, but that of adults is large, so there is no so-called fixed normal value. If it refers to the pupil diameter, the infant's pupil diameter is relatively small, generally around 1.5-2mm, while the older children or teenagers' pupil diameter is relatively large, around 3.5mm, and the old people's pupil diameter is smaller than that of the young people, around 2.5mm. If the pupil diameters of the two eyes are different, there may be optic nerve or brain diseases, which must be further examined to be clear.