Determining axis misalignment and power errors of toric soft lenses

Abstract

This article describes a method of determining the misalignment of a toric soft lens, by use of the patient's ocular refraction as well as the refraction obtained over the mislocating lens. Matrix optics are used to facilitate the calculation of the effective back vertex power of the toric lens on the eye. On the basis of this calculation, the degree of axis mislocation can be identified along with any errors in the power of the manufactured lens. The appropriate formulae are outlined and incorporated into a spreadsheet program that can be easily applied in clinical practice. Additionally, a Java applet for this purpose is accessible on the Internet at 〈http://www.optometry.unimelb.edu.au/ja..