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Zohreh Hosseinzadeh, Daniel Llewellyn Rathbun, Eberhart Zrenner; Selective activation of ON and OFF RGC input in mouse retina stimulated. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4989.
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© ARVO (1962-2015); The Authors (2016-present)
Electronic retinal implants have been developed to restore visual function in patients who suffer from retinitis pigmentosa and macular degeneration, leading to loss of photoreceptor function and blindness. The Retina Implant Alpha AMS implant developed in Germany has shown the best patient performance of any implant so far, however, patient performance still falls short of the widely accepted threshold for legal blindness of 20/200. One possibility for improving vision by enhancing contrast is to selectively activate the ON and OFF information channels of the eye. Therefore, we are studying selective electrical activation of defined retinal ganglion cell (RGC) types.
We tested amplitude-modulated electrical pulse trains for differential activation of the ON and OFF pathways. Such activation was examined in both blind and healthy mouse retina using a microelectrode array (MEA) to record and stimulate epiretinally. To characterize the stimulated ON and OFF RGCs, visual stimulation, presynaptic currents, and morphological classification were used.
Noise-embedded, sine-wave, pulse train modulations were sufficient to elicit ON or OFF RGC-specific activation, depending on the direction of the modulation (decreasing or increasing cathodic pulse amplitude, respectively). RGCs receiving ON pathway input responded more strongly to upward cathodic pulse train modulations, whereas RGCs receiving OFF input responded more strongly to downward modulations.
Deriving amplitude-modulated electrical pulse trains from the electrical input filter is a useful method to find out specific stimuli eliciting ON and OFF RGC pathway inputs. Eventually, by proving that pathway-specific activation via the implant is possible, we hope to foster the development of new retinal implants that integrate the natural visual coding used in healthy eyes.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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