Optically, why are circular eyeglasses lenses better than rectangular?

Question

https://physics.codidact.com/posts/286644

In: 10

Answer 1

Lenses to correct myopia (near-sightedness) are concave. This means the center of the lens is thinner than the edges.

The further out from the center, the thicker the glass is due to the concave curvature. A rectangular lens’s corners stick out much further from the center than a circular lens’s edges. This means that the rectangular lens can have very thick edges near the corners which makes it difficult to fit in frames, can reflect unwanted light from that wide surface, and may need to be bevelled since the edge is sharp!