Prosthetic vision in blind human patients: Predicting the percepts of epiretinal stimulation

Over the last 8 years it has been shown that an implantable retinal prosthesis can partially restore visual capabilities to blind humans. With current electrode arrays it is only possible to stimulate groups of cells rather than individual single cells with spatio-temporal precision. While artificial vision from a retinal prosthesis is unable to completely replicate the neural response patterns of normal vision, by stimulating groups of cells with electrodes patients see electrically elicited visual percepts. Thus this work will focus mainly on the form of percepts created with single electrodes in a prosthesis given certain varying stimulation parameters, and the development of a model to predict how stimuli applied produce certain percepts with single and paired prosthesis electrodes.;Ideally we would want this model to resemble a digital display with independent pixels in order to individually control each percept seen by the subject in relation to the stimuli. We find however that the model that best fits the data does not resemble a digital display but instead the nerve fiber bundle trajectories in the human retina.;The work presented here gives insight into the factors affecting form perception with a microelectronic retinal prosthesis. Specifically, by directly measuring the shapes of visual percepts from single and paired electrodes at different stimulation parameters, the building blocks of prosthetic vision are understood. The incentive is that we can use this information to develop a strategy that can control the percepts from each individual prosthesis electrode and piece them together in an organized way to best represent the visual world.