Biomimetic models of the human eye, and their applications.

Replicating the functionality of the human eye has been a challenge for more than a century, creating a great wealth of biomimetic and bioinspired devices, and providing ever improving models of the eye for myriad research purposes. As improvements in microelectronics have proceeded, individual components of the eye have been replicated, and models of the optical behaviour of the eye have improved. This review explores both work developed for improving medical components, with an ultimate aim of a fully functioning prosthetic eye, and work looking at improving existing devices through biomimetic means. It is hoped that this holistic approach to the subject will aid in the cross pollination of ideas between the two research foci. The review starts by summarising the reported measurements of optical parameters of various components of the eye. It then charts the development of individual bionic components. Particular focus is put on the development of bionic and biomimetic forms of the two main adaptive components of the eye, namely the lens and the iris, and the challenges faced in modelling the light sensitive retina. Work on each of these components is thoroughly reviewed, including an overview of the principles behind the many different approaches used to mimic the functionality, and discussion of the pros and cons of each approach. This is concluded by an overview of several reported models of the complete or semi-complete eye, including details of the components used and a summary of the models' functionality. Finally, some consideration is given to the direction of travel of this field of research, and which existing approaches are likely to bring us closer to the long term goal of a fully functional analogue of the eye.