Spatially restricted electrical activation of retinal ganglion cells in the rabbit retina by hexapolar electrode return configuration

Journal of Neural Engineering
Amgad HabibJohn W Morley


Visual prostheses currently in development aim to restore some form of vision to patients suffering from diseases such as age-related macular degeneration and retinitis pigmentosa. Most rely on electrically stimulating inner retinal cells via electrodes implanted on or near the retina, resulting in percepts of light termed 'phosphenes'. Activation of spatially distinct populations of cells in the retina is key for pattern vision to be produced. To achieve this, the electrical stimulation must be localized, activating cells only in the direct vicinity of the stimulating electrode(s). With this goal in mind, a hexagonal return (hexapolar) configuration has been proposed as an alternative to the traditional monopolar or bipolar return configurations for electrically stimulating the retina. This study investigated the efficacy of the hexapolar configuration in localizing the activation of retinal ganglion cells (RGCs), compared to a monopolar configuration. Patch-clamp electrophysiology was used to measure the activation thresholds of RGCs in whole-mount rabbit retina to monopolar and hexapolar electrical stimulation, applied subretinally. Hexapolar activation thresholds for RGCs located outside the hex guard were found to be signi...Continue Reading


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Related Concepts

Nerve Impulses
Implantable Stimulation Electrodes
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Medical Device Design
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