What does the term "pupillary distance" refer to?

Pupillary distance refers to the measurement between the centers of the pupils of the eyes. This measurement is crucial in optics and optometry as it ensures that lenses are properly aligned with the pupils, allowing for optimal vision correction and comfort in eyewear. Accurate pupillary distance helps in the fitting of various types of lenses, including single vision and multifocal lenses, as it takes into consideration the individual anatomy of the wearer. This measurement is particularly important when creating custom eyewear, ensuring that the optical centers of the lenses align perfectly with the pupils to enhance visual clarity and reduce eye strain.