These contact lenses are used to either highlight or change the colour of the iris of a healthy eye. Those that aim to achieve dramatic expression or major change of image are sometimes called “crazy lenses”. Besides the beautification function, they also fulfil prosthetic functions in the case of aniridia, of large colobom of the iris, for overlapping scars on the cornea, or for leucoms. In these cases they aim to improve the look of a damaged eye or visual function. If possible, soft contact lenses are used.