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J. A. Mocko, V. T. Ciavatta, M. K. Kim, M. H. Aung, M. T. Pardue; Effects of Different Treatment Regimens of Subretinal Electrical Stimulation on the Retinal Function in RCS Rat Retinae. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4518.
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It has been previously shown that electrical stimulation from a subretinal implanted microphotodiode array (MPA) promotes preservation of function in the degenerating retina of RCS rats. We have previously shown a dose response to both visible light and infrared (IR) stimulation. In this study, we examined interaction of frequency of treatment and different IR intensities on the dose response of subretinal electrical stimulation by the MPA.
RCS rats (n=38) underwent subretinal implantation surgery at P21 with MPA devices (Optobionics Corp.) in one randomly selected eye, and the other eye served as control. Control animals that did not undergo surgery (n=13) were also studied. All animals were divided into 4 treatment groups: high IR (60 mW/cm2) once per week, low IR (20 mW/cm2) once per week, low IR three times per week, and no IR stimulation. Implanted eyes and the left eyes of control animals were stimulated for 30 minutes per session, and all animals were followed for 4 weeks. Animals received weekly binocular ERGs, and scotopic electroretinogram (ERG) data was assessed at the 4 week time point.
B-wave amplitudes in MPA implanted eyes with high IR treatment were significantly higher than any other treatment group for brighter flash intensities (P<0.01). MPA implanted eyes with low IR treatment showed no significant differences for number of stimulations per week. There were no significant differences between implanted eyes receiving low IR and no IR stimulation, though these eyes tended to have larger b-wave amplitudes than controls. Finally, a-wave amplitudes were only significantly larger in the high IR group than the controls at the brightest flash intensities (P<0.001). ERG results showed no significant difference between non-stimulated eyes in all animals and stimulated non-implanted eyes, thus these were pooled as controls for statistical analysis.
The dose response nature of subretinal electrical stimulation by the MPAs seems to be most responsive to the intensity of the IR stimulation rather than frequency of treatment.
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