THE MECHANISM OF CONTACT LENS ADHERENCE AND CENTRALIZATION*

Abstract

At the edge of a contact lens, the tear fluid interface is concave. The radius of curvature of this interface was measured on female subjects, using a slit lamp photographic technique, and the corresponding negative pressure was calculated. When the lens is pulled by an external force, negative pressure draws the lens to the cornea. Adherence of the lens to the cornea is thus achieved by negative pressure. To move the lens to the flatter peripheral cornea, the lens must be lifted against negative pressure; negative pressure draws the lens back to the optical zone of the cornea. Thus both adherence and centralization are accomplished by means of negative pressure.