Pupillary distance (PD)

The pupil distance of the eye is generally 55-75cm, which is the distance between pupils. When the eyes are looking straight ahead, the distance between the center of the pupil and the center of the pupil is the interpupillary distance. Pupil distance varies according to the development of each person and the size of the face. According to the differences between Chinese and foreigners, pupil distance varies greatly. Generally, however, the pupillary distance does not have much influence on the visual function of eyes.

When fitting glasses, there is an optical center of the glasses, and the optical centers of the two glasses must be consistent with the interpupillary distance, so that the vision can obtain effective refractive symmetry. At the same time, the interpupillary distance can play a role in the lesions. For example, the interpupillary distance of patients with esotropia will become smaller, and the light spot can be found according to the fluorescent spot, and then the degree of strabismus can be found. The interpupillary distance of exotropia can be increased, and the degree of strabismus can be judged according to the distance between the center of cornea and the distance between fluorescent spots. Therefore, the interpupillary distance can play a certain diagnostic assistant role in glasses and strabismus.