Characterization of retinal tissue and vitreous humor with Electrical Impedance Spectroscopy

Electrical impedance spectroscopy is used to study the retina and the vitreous humor which can help in designing retinal stimulation experiments. Electrical stimulation of retina is done to artificially stimulate retinal neurons for restoring vision in blind patients. The stimulus is given through microelectrodes which are placed over the retina. Since retina is an inhomogeneous conductive medium with ionic species as charge carriers, electrical characterization of the retina as well as the tissue interface is required. Vitreous humor comes in between tissue and electrode which has properties different from that of retina. Change in vitreous properties can alter the experimental results for stimulation of the retina. Thus calculation of electrical properties of both vitreous and retinal tissue are necessary for designing of stimulus parameters. Goat retina is used in this study for characterization which can help in further using this animal in stimulation experiments. It has been found that the RGC side of isolated retina has lower resistance to current flow compared to the photoreceptor side. It has also been found that changes in the vitreous properties that might affect the tissue stimulation parameters can be measured through impedance spectroscopy.