瞳距一般是指人正常平视事物时，瞳孔间的距离。

对于近视眼或者远视眼患者，配眼镜时，需要考虑这个参数。即两块镜片中心的距离应当与患者的瞳距相配合，否则，即使度数正确，患者戴上眼镜后也会有不适的感觉，并且影响视力。

Pupillary Distance (PD) or interpupillary distance (IPD) is the distance (the industry standard is to measure in millimeters) between the centers of the pupils in each eye. This measurement is used when preparing to make prescription eyeglasses. Positioning lenses correctly in relation to the centre of the pupils is especially important for higher powered lenses due to the location of the optical centre of the lenses. It can also be relevant to binoculars: they must be adjusted to suit the user's IPD; and the minimum allowed by some binoculars is still too great for people with a small IPD.