Step-by-Step Procedure to Test Photoelectric Dye-Coupled Polyethylene Film as Retinal Prosthesis to Induce Light-Evoked Spikes in Isolated Retinal Dystrophic Tissue of rd1 Mice

Purpose: Multielectrode array recording for electric activity in cardiac and neuronal cells has been developed as preclinical tests for drug screening. This study aims to establish an in vitro assay system, using the multielectrode array, to record light-evoked spikes in isolated degenerative retinal tissues of retinal dystrophic rd1 mouse, as a preclinical test to examine the efficacy of photoelectric dye-coupled thin film retinal prosthesis. Methods: Light-evoked spike response was tested for 1 min at first step in the isolated degenerative retinal tissue of retinal dystrophic rd1 mouse only on the multielectrode array, tested in the same retinal tissue overlain with a plain control film for light-off and light-on 10 min each at second step, and tested in the same tissue overlain with a dye-coupled film at third step. The retinal tissues which showed light-evoked response at first or second step were not used for evaluation at third step. Results: Residual light-evoked spikes were recorded at first or second step in 18 of 35 retinal tissues (51%) at 6 weeks of the age in rd1 mice, 16 of 44 tissues (36%) at 7 weeks, and 10 of 39 tissues (25%) at 8 weeks. At third step, light-evoked spikes were recorded with dye-coupled films in 8 of 17 retinal tissues (47%) at 6 weeks, 10 of 28 tissues (35%) at 7 weeks, and 8 of 29 tissues (27%) at 8 weeks. Conclusion: A step-by-step procedure with internal control was established to measure light-evoked spikes by the multielectrode array in the isolated degenerative retinal tissue to evaluate photoelectric dye-coupled thin films. This preclinical study would present one line of evidence for the efficacy of photoelectric dye-coupled thin film retinal prosthesis towards a first-in-human clinical trial