Our online calculator, based on the Castrop formula, assists ophthalmic surgeons in selecting the individual IOL power in cataract surgery. It is intended to be used in conjunction with a comprehensive ophthalmic examination and the appropriate diagnostic tests and measurements required for candidates for cataract surgery. The results obtained with the calculator are not intended as medical or surgical guidance and cannot be considered definitive, nor can the results be guaranteed to be accurate in every case. Physicians using the calculator must make their own independent decisions about the correct treatment for their patients and are solely responsible for the outcome of the refraction. Furthermore, the information about our Castrop formula IOL calculator, available on this website, is provided without warranty of any kind, either explicit or implicit. Our online calculator is subject to copyright and other intellectual property rights under German and foreign laws and international conventions. It may not be copied, imitated, or used, in whole or in part, without the prior written permission of Prof. Dr. Achim Langenbucher and Dr. Peter Hoffmann.