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, it can lead to induced prism effects. This occurs because the lenses are not positioned correctly in relation to the line of sight. Each eye has a specific point where it sees best, known as the optical center. If the optical centers are displaced from the patient's pupillary distance, the light passing through the lenses will bend inappropriately, creating a prism effect that can cause visual disturbances such as double vision or blurred vision.

Induced prism can lead to discomfort and visual fatigue as the brain tries to reconcile the differences in the images being processed from each eye. Correctly aligning the optical centers with the pupillary distance is essential for optimizing vision and comfort, making this the crucial reason to ensure proper fitting of spectacles.

The other conditions mentioned, such as astigmatism, hyperopia, and myopia, are refractive errors that are generally caused by the shape of the eye rather than misalignment of the optical centers. These refractive issues occur independently of how the spectacles are aligned and are not a direct consequence of the misalignment of optical centers.