This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Vision is initiated by absorptions in the photoreceptors within the retina. Beginning with the output neurons of the retina, the ganglion cells, a series of long range white matter tracts communicate visual signals to the visual cortex. These white matter structures in the early visual pathways can be reliably identified using diffusion-tensor imaging (DTI) and fiber tractography. The clinical use of DTI in Ophthalmology is limited by the lack of a normal standard of reference.