What can occur if the optical centers of spectacles are not aligned with the patient's pupillary distance?

When the optical centers of spectacles are misaligned with the patient's pupillary distance (PD), one significant outcome is the induction of prism. Spectacles are designed to provide the best visual experience when their optical centers align precisely with the wearer's eyes. If they do not, the light passing through the lenses is deviated from the intended path, creating a prism effect.

Induced prism can lead to a variety of visual issues, such as double vision or discomfort, as the eyes must work harder to compensate for this misalignment. In essence, the visual system may struggle to fuse images properly, leading to undue strain, which can result in a diminished visual quality. Thus, ensuring the correct alignment of optical centers with the pupillary distance is critical to provide optimal vision correction and comfort.