Cataract is an opacity of the ocular lens, often occurring at mature age. Apart from ageing it can be caused by - among other things - metabolical disorders, trauma, and infrared or ultraviolet light. Globally, cataract is one of the main causes of blindness. Already for more than 2500 years cataract operations have been performed. During the last 25 years both the operation and the implantation of artificial lenses have been brought to great perfection. This means that one of the prominent spoilers of a good old age is to a large degree controllable.