Role of Gravity in Prism Ballasting

One of the techniques commonly used in stabilizing the rotation of a contact lens is prism ballasting. The idea is to gain stabilization by the action of gravity pulling on the base of the prism. The determination of just how much prism is necessary in any particular case is usually made empirically, gradually increasing prism amount when more stability is required. This paper will present the results of a mathematical investigation which demonstrates that gravity forces alone do not play the major role in the stabilization of prism ballasted lenses. It is hoped that this preliminary analysis will stimulate further theoretical work of a similar nature, in the growing field of contact lenses.