What will excessive tilting of a lens cause?

Excessive tilting of a contact lens primarily leads to marginal astigmatism. When a lens is tilted, the position of the optical axis shifts, resulting in the disparity of light entering the eye through different meridians. This misalignment can create variations in the effective power of the lens, which simulates astigmatism.

Marginal astigmatism arises because the tilt changes how the light focuses on the retina, causing blurriness or distortion in vision. This phenomenon occurs because, in a tilted lens, different parts of the lens bring light to focus at different distances, akin to the effects of pathological astigmatism. It emphasizes the importance of maintaining proper lens positioning for optimal visual acuity and comfort.

While the other options may also relate to lens performance, they are not the direct consequence of excessive lens tilting. For instance, added power can occur with changes in lens thickness or curvature rather than tilting, distortion generally refers to image shape changes not directly tied to tilt, and spherical aberration is a type of optical aberration not specifically induced by lens tilt.