Note how the bottom edge of the lens is against the lower eye lid. If the wearer looks down, the lens is pushed up a little. This "trick" can be used to provide bifocal contact lenses. These lenses have different powers in the center than in the periphery. When the wearer looks down to read the lens is moved to a new position to facilitate seeing sharply at normal reading distances.
If there is an irregularity on the cornea (astigmatism) it is automatically corrected by the combination of the tear layer and the contact lens.
Table of Contents
Table of Contents [When not using frames]