"Despite extensive research on the optics of the eye and the neuronal processing of the optical image that is projected on the retina, a number of basic questions are surprisingly unclear. Combining the expertise of 5 University-based European laboratories with a long history of scientific accomplishments, a well established industrial partner, and a high-ranking international advisory board, this training network will provide a platform to train young natural scientists at the interface of physics, optics and biology. Several of the PIs were successfully involved in previous multi-site training activities. Training activities will include complementary skills courses, lab exchanges, external schools and network meetings. The proposed research projects will elucidate the limits of visual performance, using state of the art technology. It has direct implications for optical correction strategies (spectacles, refractive surgery etc), for the understanding how different mono- and polychromatic aberrations limit vision and sensitivity in low light environments. In addition, the research will improve the understanding of the cues that drive accommodation and emmetropization, the mechanisms by which neural processing in the eye can ""sharpen"" degraded, aberrated or defocused retinal images, and how visual performance is affected by diurnal factors. The combination of expertise of the PIs in physics, optics and biology (probably unique in Europe) will provide the young scientists with knowledge that opens the doors to positions in Medical Optics Industry as well as positions in Academia. Furthermore, the young scientists will be extensively exposed to specialists in the field who have well-established contacts to the private sector, opening the door for long-term interactions."