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 not aligned with the patient’s pupillary distance, it can lead to the occurrence of induced prism. This misalignment is crucial because each eye has a specific point at which light must enter the lens to be most effective for vision correction. If the optical center of the lens differs from the pupillary distance, the light entering the lenses can bend away from the desired focal point, creating a prism effect.

This induced prism can cause visual discomfort, double vision, or blurred vision, as the brain struggles to fuse the images from each eye effectively. Proper alignment ensures that the optical center correlates with the natural position of the pupil, allowing for accurate vision correction without unnecessary strain on the visual system. This highlights the importance of precise measurements in eyewear fitting and the critical role of the pupillary distance in the lens prescription process.