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In the last decade several groups have been developing vision prostheses to restore visual perception to the profoundly blind. Despite some promising results from human trials, further understanding of the neural mechanisms involved is crucial for improving the efficacy of these devices. One of the techniques involves placing stimulating electrodes in the(More)
Recipients of vision prosthesis prototypes have reported electrically elicited visual perceptions as discrete dots of light (phosphenes). Phosphenes construct the scenery in discontinuous small isolated patches, resulting in visual information deficit to a large portion of the visual field. Visual scanning therefore plays an important role in the utility of(More)
With increasing research advances and clinical trials of visual prostheses, there is significant demand to better understand the perceptual and psychophysical aspects of prosthetic vision. In prosthetic vision a visual scene is composed of relatively large, isolated, spots of light so-called "phosphenes", very much like a magnified pictorial print. The(More)
100-channel neurostimulation circuit comprising a complementary metal oxide semiconductor (CMOS), application-specific integrated circuit (ASIC) has been designed, constructed and tested. The ASIC forms a significant milestone and an integral component of a 100-electrode neurostimulation system being developed by the authors. The system comprises an(More)
Acceptance of prosthetic vision will be heavily dependent on the ability of recipients to form useful information from such vision. Training strategies to accelerate learning and maximize visual comprehension would need to be designed in the light of the factors affecting human learning under prosthetic vision. Some of these potential factors were examined(More)
A virtual-reality simulation tested prosthetic visual acuity for both rectangular and hexagonal phosphene grids. Thirteen normally sighted, untrained subjects were required to identify the Landolt C optotype over ten sessions. Overall performance, performance by filter setting (image analysis), and performance by size and orientation of the Landolt C(More)
A neurostimulator application-specific integrated circuit (ASIC) with scalable circuitry that can stimulate 14 channels, has been developed for an epi-retinal vision prosthesis. This ASIC was designed to allow seven identical units to be connected to control up to 98 channels, with the ability to stimulate 14 electrodes simultaneously. The neurostimulator(More)
Investigators of microelectronic visual prosthesis devices have found that some aspects of vision can be restored in the form of spots of light in the visual field, so-called "phosphenes", from which more rich and complex scenes may be composed. However, questions still surround the capabilities of how such a form of vision can allow its recipients to "see"(More)
By way of extracellular, electrical stimulation of the visual pathway, the various approaches to vision prosthesis aim to provide crude, patterned vision to individuals with profound blindness. Common to all approaches is the implantable electrode array and the rendering of phosphenes-the actuated percepts occupying the visual field of the implantee. Thus(More)
Several approaches have been proposed for placement of retinal prostheses: epiretinal, subretinal and suprachoroidal. We aimed to systematically evaluate the effectiveness of varying a range of stimulus parameters and electrode geometry for a suprachoroidal electrode array, using cortical evoked responses to monopolar electrical stimulation in cats. Our(More)