All Publications

  • Characterization of an Electronic Corneal Prosthesis System. Current eye research Shim, S. Y., Gong, S., Fan, V. H., Rosenblatt, M. I., Al-Qahtani, A. F., Sun, M. G., Zhou, Q., Kanu, L., Vieira, I. V., Yu, C. Q. 2019


    PurposeCorneal opacity is a leading cause of reversible blindness worldwide. An electronic corneal prosthesis, or intraocular projector, could potentially restore high-quality vision without need for corneal clarity.Materials and MethodsFour intraocular projection systems were constructed from commercially available electronic components and encased in biocompatible plastic housing. They were tested for optical properties, biocompatibility, heat dissipation, waterproofing and accelerated wear. A surgical implantation technique was developed.ResultsIntraocular projectors were produced of a size that can fit within the eye. Their optics produce better than 20/200 equivalent visual acuity. MTT assay demonstrated no cytotoxicity of devices in vitro. Temperature testing demonstrated less than 2 C increase in temperature after one hour. 3 devices lasted over 12 weeks under accelerated wear conditions. Implantation surgery was demonstrated via corneal trephination insertion in a cadaver eye.ConclusionThis is the first study to demonstrate and characterize fully functional intraocular projection systems. This technology has the potential to be an important new tool in the treatment of intractable corneal blindness.

    View details for DOI 10.1080/02713683.2019.1708957

    View details for PubMedID 31886728

  • Intraocular microdisplay projection system for treating corneal blindness Fan, V., Rosenblatt, M., Sun, M., Yu, C. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2019
  • Epiretinal stimulation with local returns enhances selectivity at cellular resolution JOURNAL OF NEURAL ENGINEERING Fan, V. H., Grosberg, L. E., Madugula, S. S., Hottowy, P., Dabrowski, W., Sher, A., Litke, A. M., Chichilnisky, E. J. 2019; 16 (2)
  • Optimizing Selectivity of Epiretinal Stimulation using Local Returns Fan, V., Grosberg, L. E., Madugula, S., Hottowy, P., Dabrowski, W., Sher, A., Litke, A. M., Chichilnisky, E. J. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2017
  • Activation of ganglion cells and axon bundles using epiretinal electrical stimulation. Journal of neurophysiology Grosberg, L. E., Ganesan, K., Goetz, G. A., Madugula, S. S., Bhaskhar, N., Fan, V., Li, P., Hottowy, P., Dabrowski, W., Sher, A., Litke, A. M., Mitra, S., Chichilnisky, E. J. 2017: jn 00750 2016-?


    Epiretinal prostheses for treating blindness activate axon bundles, causing large, arc-shaped visual percepts that limit the quality of artificial vision. Improving the function of epiretinal prostheses therefore requires understanding and avoiding axon bundle activation. This paper introduces a method to detect axon bundle activation based on its electrical signature, and uses the method to test whether epiretinal stimulation can directly elicit spikes in individual retinal ganglion cells without activating nearby axon bundles. Combined electrical stimulation and recording from isolated primate retina were performed using a custom multi-electrode system (512 electrodes, 10 ?m diameter, 60 ?m pitch). Axon bundle signals were identified by their bi-directional propagation, speed, and increasing amplitude as a function of stimulation current. The threshold for bundle activation varied across electrodes and retinas, and was in the same range as the threshold for activating retinal ganglion cells near their somas. In the peripheral retina, 45% of electrodes that activated individual ganglion cells (17% of all electrodes) did so without activating bundles. This permitted selective activation of 21% of recorded ganglion cells (7% of all ganglion cells) over the array. In the central retina, 75% of electrodes that activated individual ganglion cells (16% of all electrodes) did so without activating bundles. The ability to selectively activate a subset of retinal ganglion cells without axon bundles suggests a possible novel architecture for future epiretinal prostheses.

    View details for DOI 10.1152/jn.00750.2016

    View details for PubMedID 28566464

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