title: Evaluation of Effects of Electrical Stimulation in the Retina with Optical Coherence Tomography.
abstract: Retinal prostheses provide the capability to blind patients to detect motion and locate large objects. To avoid activating axons of passage, which can create streak-like perceptions, long pulse stimulation can be used to bypass axons and achieve focal retinal activation. Safety is a concern because long pulses require more charge than short pulses to elicit a response from neural tissue. Future implants will require smaller electrodes to improve resolution, but increased charge density may result, which is another safety concern. We developed a method to study the effects of electrical stimulation in the retina in real time using OCT (Optical Coherence Tomography) imaging combined with micropositioning of a stimulating electrode over the retina in an animal model. When using a 250-micron diameter electrode and stimulating for 30 minutes (frequency: 333 Hz), charge density: 1.22 mC/cm2, we observed an increase in retinal thickness from 154.3μm± 7.04μmto 179.67μm± 0.47μm, a 16.66 % ± 5.49% increase compared to baseline. The region of increased thickness extended laterally for 0.56 mm ± 0.009 mm. When stimulating with a charge density of 1.63 mC/cm2, we observed an increase in retinal thickness from 160.3μm± 2.05μmto 190μm± 0.81μm, a 19.52 % ± 1.86% increase compared to baseline. The region of increased thickness expanded laterally for 1.27 mm ± 0.19 mm.
authors.affiliation: Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA.
authors.forename: A
authors.initials: A
authors.lastname: Gonzalez-Calle
authors.affiliation: Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA and Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Weiland
mesh_terms: D000818:Animals; D004558:Electric Stimulation / Q000379:methods*; D004566:Electrodes; D006801:Humans; D011817:Rabbits; D012160:Retina / Q000502:physiology*; D041623:Tomography, Optical Coherence / Q000379:methods*