PD is the abbreviation of pupillary distance, which means pupillary distance. Pupil distance refers to the distance between the center lines of eyeball pupils. Usually, the pupillary distance measured by adults is between 54 and 74 mm, but there are also individual differences. The purpose of measuring PD is to put glasses on eyes correctly to achieve the best visual effect and comfort.

PD is one of the most important parameters for buying glasses. If you wear the wrong size glasses, it will cause discomfort and visual problems. If the pupil spacing of glasses is too small, the visual range will be reduced after wearing glasses; If the distance between pupils is too large, ghosting or distortion will occur. Therefore, measuring PD is a necessary step to ensure proper size, good comfort and good visual effect of glasses.

There are many methods to measure PD, but PD meter is the most commonly used one. Generally speaking, people usually go to an optical shop or an ophthalmologist for measurement, but they can also use special measuring instruments at home. It should be noted that the comfort and visual effect of glasses are closely related to the accuracy of PD, so we suggest that the measurement should be carried out under the guidance of professionals as much as possible.