When lens centers are ground wider than the pupil distance, what is the prismatic effect for the wearer?

When lens centers are ground wider than the pupil distance, this setup results in a prismatic effect known as "base in." This occurs because the lenses are positioned in such a manner that they cause light to bend towards the nasal side of the lens, thereby creating a prismatic effect that moves the image towards the midline of the wearer's vision.

This is particularly relevant when understanding how optical alignment relates to the positioning of the lenses relative to the pupil centers. If the lenses are ground too wide, it leads to a situation where light enters the lenses further away from the point where the pupil is positioned, creating a discrepancy that effectively shifts the visual image towards the center. The phenomenon is crucial for optical prescriptions and understanding how adjustments in lens measurements can impact the visual experience for the wearer.