Final answer:
Image size changes less with contact lenses than with spectacles because contacts move with the eye, offer better peripheral vision, and correct corneal astigmatism through the tear layer acting as part of the optical system.
Step-by-step explanation:
The change in image size with contact lenses is less pronounced compared to spectacles because contact lenses sit directly on the cornea and move with the eye. This provides multiple benefits, such as superior peripheral vision, and correction of some corneal astigmatism. The tear layer that forms between the contact lens and the cornea can fill in surface irregularities, creating a more regular optical surface, which can lead to a more accurate refraction of light onto the retina. Furthermore, the index of refraction of the tear layer is very similar to that of the cornea, enhancing the optical experience. Optometrists can customize the curvature and power of contact lenses to compensate for any irregularities, providing clearer vision.