Marc Patrick H. Zapf

Learn More
The feasibility of implants for prosthetic vision has been demonstrated by research and commercial organizations. In most devices, an essential forerunner to the internal stimulation circuit is an external electronics solution for capturing, processing and relaying image information as well as extracting useful features from the scene surrounding the(More)
OBJECTIVE The prospective efficacy of a future peripheral retinal prosthesis complementing residual vision to raise mobility performance in non-end stage retinitis pigmentosa (RP) was evaluated using simulated prosthetic vision (SPV). APPROACH Normally sighted volunteers were fitted with a wide-angle head-mounted display and carried out mobility tasks in(More)
Introduction: In the last decades, advances have been made in the development of so-called scale space approaches to search for brain responses in imaging data such as from functional magnetic resonance imaging In these approaches, responses are statistically detected using a range of Gaussian filter widths instead of using a single one. Despite the(More)
OBJECTIVE The prospective efficacy of peripheral retinal prostheses for guiding orientation and mobility in the absence of residual vision, as compared to an implant for the central visual field (VF), was evaluated using simulated prosthetic vision (SPV). APPROACH Sighted volunteers wearing a head-mounted display performed an obstacle circumvention task(More)
Introduction: Recently, a functional magnetic resonance imaging (fMRI) analysis approach involving surface-based (2D) smoothing of hand-segmented brain slices has been developed (see companion poster, Kilias et al.). Unlike traditional volume-based (3D) filtering, which uses euclidean distances to determine neighborship relations between voxels in the brain(More)
Simulated prosthetic vision (SPV) in normally sighted subjects is an established way of investigating the prospective efficacy of visual prosthesis designs in visually guided tasks such as mobility. To perform meaningful SPV mobility studies in computer-based environments, a credible representation of both the virtual scene to navigate and the experienced(More)
Retinal implants have proven their ability to restore visual sensation to people with degenerative retinopathy, characterized by photoreceptor cell death and the retina's inability to sense light. Retinal bionics operate by electrically stimulating the surviving neurons in the retina, thus triggering the transfer of visual sensory information to the brain.(More)
Retinitis pigmentosa (RP) causes visual field (VF) constriction due to progressive loss of photoreceptors, typically from the retinal periphery to the fovea. Retinal prostheses offer vision restoration via electrode implantation and stimulation near the fovea, thereby eliciting articifial percepts, so-called phosphenes in the center VF. Although foveal(More)
  • 1