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Objective: We examined whether electrical stimulation efficiency is affected by specific patterns of pathological spontaneous activity observed in mouse models of retinal degeneration. Materials and Methods: Using a multielectrode array system, we applied biphasic current pulses to retinae of wild[for full text, please go to the a.m. URL], Artificial Vision 2017

In degenerative diseases of the retina, like retinitis pigmentosa (RP), the loss of photoreceptors is followed by a remodeling process of the remaining inner retina and blindness. Retinal prostheses are used to restore vision in RP patients through electrical stimulation but current models of prostheses are not adjusted to the changes of the remodeling process. In vitro multielectrode array (MEA) recordings from retinae of a genetic model (retinal degeneration 10, rd10) and a pharmacologically-induced model (N-methyl-N-nitrosourea (MNU) treatment) of retinal degeneration were compared with recordings from healthy retinae of wild type (wt) mice. In addition to the investigation of the spontaneous activity, retinae were stimulated with biphasic current pulses of different amplitudes and durations. In contrast to wt retinae, degenerated retinae showed oscillatory potentials and rhythmic spiking in a burst formation. In many cases, bursts were found phase-locked to the minima of the oscillations. The oscillations occured at frequencies of 3-6 Hz in rd10 retinae and of 6-9 Hz in retinae of MNU-treated mice. In all age groups, electrical stimulation was more effective in wt retinae than in retinae of both degeneration models. In the presence of bursts or oscillations, the stimulation efficiency of ganglion cells was particularly low. Low stimulation efficiency would impair the use of retinal prostheses. In order to increase stimulation efficiency in degenerated retinae, two methods were investigated that might abolish the abnormal activity. Application of an electrical pre-stimulus inhibited bursts and oscillations such that the activity resembled the activity of a wt retina. Furthermore, retinae were perfused with different drugs. Meclofenamic acid (MFA), a blocker of electrical synapses, also abolished oscillations occasionally. Although, neither the pre-stimulus method nor the pharmacological method reliably increased stimulation efficiency, the preliminary results encourage to continue with this approach.The results reveal obvious differences between electrophysiological properties of healthy and degenerated retinae and therefore confirm the necessity to consider retinal changes occurring during degeneration in the development of new retinal prostheses.