Lens Form

Question 1

Define: Spherical lenses

Answer 1

A spherical lens is a lens whose surface has the shape of (part of) the surface of a sphere.

Question 2

Define: base curve in ophthalmic lenses

Answer 2

The base curve of a lens is the surface curve that serves as the basis or starting point from which the remaining curves will be calculated.

Question 3

What is meant by flat and curved in ophthalmic lenses

Answer 3

Flat lenses: lens whose flat shape allows it to provide distortion-free image and refers to lenses that provide a negative index of refraction.

Curved lenses: lenses formed by binding two spherical surfaces, if bulging outward then convex (-). If curved inwards then concave (+).