Re: How do contact lenses adjust eye sight?

Most light is refracted by the cornea as light passes from air (low density) to the corneal tissue (higher density).

The lens of the eye also can be made thinner or thicker and rounder by cables called zonules that pull on its edge. This lets our eyes focus on far objects (thinner lens) and near objects (thicker rounder lens)by making fine changes to the refraction of light.

If the eye ball is too long or too short, we cannot focus light on the retina for near or far objects.

The first diagram shows a near sighted eye, and the second diagram shows the effect of placing a contact lens of correct power onto the cornea. The lens alters the incoming light path in the required direction so that the end focus of light can fall onto the retina.

That is the basic idea. :)

Ken Mitton, PhD
a Canuck at the
Kellogg Eye Center
University of Michigan Medical Center