PD, which is short for pupillary distance and sometimes is also called the interpupillary distance, or IPD, refers to the distance between the centers of the pupils in each one of the eyes of human beings. When people are preparing to choose their own prescription eyeglasses, the doctor will take the measurement of their PD in order to make sure that the lenses can be positioned lenses correctly in relation to the centre of the pupils of eyes and to ensure the correct centration of your prescription lenses in front of your eyes. This measurement is especially important for people who have to wear higher powered lenses, which is because that the location of the optical centre of the lenses should be adjusted to suit the user's IPD. This just can also be relevant to binoculars. Children, adults, females and males all have different pupillary distances, and the typical pupillary distance for adults is around 54 to 68 mm, while measurements generally fall between 48 and 73 mm.
PD, so-called pupillary distance, is the distance between the center of your pupils, ranging typically between 57 and 65 mm. PD is necessary when you buy prescription eyeglasses, including distance PD and near PD. I mean, when you look straight ahead, your pupils keeps a slight larger distance, whereas this distance changes, when you look close to read because your eyes converge an average of three millimeters. In general, ordering glasses need them because it helps custom-fit your glasses lenses to focus straightly over your pupils so that your can feel better and improve the clarity of your vision . In order to ensure lenses best performance, the firgues are need to set 'optical centre', or glasses pupillary distance is not set correctly, you will inevitably suffer strain to look through them, what is worse than that, it can also cause headaches, visual distortion or even double vision. Well, get your PD during a sight test in an eye office or retail location.
Well, of course they are different from each other. Generally speaking, PD stands for "Pupillary distance" in glasses. And it is the distance between the pupil of your right eye and the pupil of your left eye. The standard measurement is taken in millimeters. When measuring a PD it is important that the eyes are still and facing forwards. A proper measurement of a PD ensures that the lenses are positioned correctly in relation to the pupil centers. On the other hand, axis describes the lens meridian that contains no cylinder power to correct astigmatism. And it is defined with a number from 1 to 180. The number 90 corresponds to the vertical meridian of the eye, and the number 180 corresponds to the horizontal meridian. So they are different from each other.