Imaging the visual system: from the eye to the brain

Imaging technologies have revolutionized the study of human anatomy and physiology. Nowhere is this more evident than in the vision sciences, where imaging has provided unprecedented insights into the structure and function of the entire visual pathway in vivo. Ocular and retinal imaging techniques such as optical coherence tomography (OCT)[1, 2] have become established clinical tools, providing highly detailed images of ocular structures that are now used routinely to support the diagnosis and management of ocular disease. The expanding scope of measurements possible with ocular imaging technology is resulting in even more accurate diagnostic and prognostic clinical instruments and progressing our understanding of the eye's structural and functional properties. On the other hand, brain imaging technologies such as functional magnetic resonance imaging[4, 5] and diffusion tensor tractography[6] are not yet widely utilized in the clinical management of visual disorders. This is likely to change. There is increasing evidence that the impact of ocular disease on visual function cannot be fully understood without considering associated changes in the structure and function of the brain.[7] Furthermore, attempts to restore vision using electrical prosthetics[8-10] or regenerative medicine[11] require an understanding of the entire visual pathway in patients with vision loss. For example, any neurodegenerative effects of long-term visual cortex deafferentation will limit the extent to which vision can be recovered when retinal input to the brain is restored. Therefore future advances in the field of vision restoration are likely to rely critically on information from a combination of both eye and brain imaging techniques. This feature issue had two main goals. The first was to identify new imaging technologies and recent progress in established imaging methodologies that can be applied to the visual system. The second was to highlight advances in our understanding of the visual system and visual disorders that have been achieved through the use of imaging techniques. These broad goals allowed us to assemble a collection of papers that span the entire visual system from the cornea to the extrastriate visual cortex.