Cataracts are the most important cause of acquired blindness worldwide. The oldest known surgical treatment for cataracts dates back to around 1,000 years before Christ. The Indian surgeon Sushruta described the technique of 'couching', in which the opaque lens is pushed from the line of vision using a needle. At the time of Alexander the Great this technique spread across Europe and then to the rest of the world. Couching was the only available treatment for cataracts for a long time, until the discovery of lens extraction by Jacques Daviel in 1748. Since then lens extraction has replaced couching in the western world, because of poor results and high complication rates. This procedure is, however, still practiced in areas of Africa and Asia.