A System for Study of Pediatric Visual Pathways

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DESCRIPTION (provided by applicant): A System for Study of the Pediatric Visual Pathways is requested by a group of Pediatric Ophthalmologists and Neonatal Neurologists. These investigators currently have NIH supported studies of retinopathy of prematurity (ROP), periventricular leukomalacia (PVL), and strabismus and amblyopia. Investigations of the visual system in subjects with albinism and known genotypes are also planned in collaboration with Genetics. The equipment requested is for visual evoked potential (VEP), eye movement and fMRI studies, and will be used to investigate function of the pathways from the eye to the brain. The information gained about function of the visual pathways will complement current assessments of structure of the eye and brain. Additionally, this information will complement the behavioral (psychophysical) assessments of vision already in progress. In the proposed ROP and PVL research, the main hypothesis under test is that preterm injury to the architecture of the visual pathway in the eye (ROP) or the optic radiations (PVL) significantly alters the inputs to the visual areas of the brain. At the earliest ages, VEP responses to diffuse flash stimuli will be evaluated as predictors of visual and neurological development. Later in infancy, longitudinal VEP acuities in ROP and PVL subjects will be the basic data upon which analysis of plasticity of their developing visual systems will be evaluated. VEP studies of misrouting of the visual pathways will be conducted in subjects with symmetrical and asymmetrical PVL. The eye movement tracker will be used to characterize their nystagmus and to verify fixation during VEP testing. Furthermore, future fMRI studies are envisioned using patterned stimuli presented quadrant by quadrant, in older, cognitively intact subjects with PVL and visual field cuts, and their peers without field cuts. The large sample of term born infants, children and adults with strabismus and amblyopia, and their unaffected peers, will have VEP acuity measured in a cross-sectional design. Eye movements during fixation and voluntary saccades will be quantified. This information, along with the clinical data, will lay the foundation for future fMRI studies of the amblyopic deficit. Finally, in collaboration with Genetics, members of families with albinism and known tyrosinase genotype, will have VEP studies of visual pathway routing using flash stimuli in infancy and patterned stimuli at older ages. Selected adult members of the families with albinism will be studied using fMRI studies employing the rotating wedge stimulus of Wandell and careful control of eye position. With these studies as a whole, we expect to obtain new knowledge about the processes that govern vision and its development in these pediatric disorders.