COMPARISON OF A VIDEOKERATOSCOPE AND AN AUTOKERATOMETER AS PREDICTORSOF THE OPTIMUM BACK SURFACE CURVES OF RIGID CORNEAL CONTACT-LENSES

Purpose: To determine the differences in the corneal topography derive d using a 16 mire videokerascope and a 2 mire autokeratometer and to e xamine whether the differences are clinically significant in the conta ct lens fitting context.Methods: The right corneas of 20 subjects were measured by an Eyesys videokeratoscope (windows workstation: version 2000 W) and a Topcon Autokeratometer (KR 3500), The corneal vertex rad ius and p-value were deduced and used to calculate the back surface sp ecifications of a rigid corneal tricurve contact lens design required for an optimal fit on the corneal model. The study was aimed to evalua te the differences in contact lens specifications related to the curre nt British Standards on contact lens tolerances. Results: In general t here was good agreement in the lens specification derived from the two instruments. The differences that were present were small and, with t he exception of the second back peripheral radius, were within toleran ce limits, Conclusions: The corneal topography was adequately describe d by the two mire keratometer for the purpose of fitting this particul ar lens design on the corneas of the 20 subjects examined. (C) 1997 Th e College of Optometrists, Published by Elsevier Science Ltd.