Comparison Of Back-Surface Aspheric, Rigid Contact Lenses: Power Distribution, Eccentricity, And Add Change.

The Corneal Analysis System was used to measure the back surface of Goldberg APA aspheric rigid multifocal contact lenses in order to calculate the contact lens ' eccentricity , average and specific. A modified lensometer stop was used to measure the power of these contact lenses at specific points at a known distance from the center of the lens to determine the change in power across the back surface of the lenses . The results showed that the change in power from the center of the lens to the edge varied based upon the eccentricity and apical radius of the lens; therefore, when fitting a patient with aspheric RGPs, the contact lens practitioner must consider the relationship between eccentricity , apical base curve, and add change.