Progress in artificial vision through suprachoroidal retinal implants

Abstract

Retinal implants have proven their ability to restore visual sensation to people with degenerative retinopathy, characterized by photoreceptor cell death and the retina's inability to sense light. Retinal bionics operate by electrically stimulating the surviving neurons in the retina, thus triggering the transfer of visual sensory information to the brain. Suprachoroidal implants were first investigated in Australia in the 1950s. In this approach, the neuromodulation hardware is positioned between the sclera and the choroid, thus providing significant surgical and safety benefits for patients, with the potential to maintain residual vision combined with the artificial input from the device. Here we review the latest advances and state of the art devices for suprachoroidal prostheses, highlight future technologies and discuss challenges and perspectives towards improved rehabilitation of vision.

Safety Studies for a 44-Channel Suprachoroidal Retinal Prosthesis: A Chronic Passive Study

“…Eight animals demonstrated good mechanical stability of the array with only minor (<2 disc diameters) lateral movement. Four cases of surgical or stability complications occurred due to (1) bulged choroid during surgery, (2) hemorrhage from a systemic bleeding disorder, (3) infection, and (4) partial erosion of thin posterior sclera. There was no change in retinal structure or function (other than that seen at surgery) at endpoint.…”

“…Keywords: retinal prosthesis, optical coherence tomography, electroretinography, retinal histology, retinal safety R etinal prostheses can restore some functional vision to patients with profound vision loss from progressive retinal degenerative diseases such as retinitis pigmentosa. [1][2][3][4] Retinitis pigmentosa affects over 1.5 million people worldwide, and is the leading cause of irreversible vision loss in a working age population. 5 Retinal prostheses bypass the degenerating photoreceptors and electrically stimulate the remaining intact neurons in the inner retina, including the bipolar cells and the retinal ganglion cells.…”

“…Hence, we have now upgraded the retinal prosthesis to a 44-channel electrode array, both increasing the number of electrodes and the field of view. There are two key design changes from our previous prototype arrays 24,27,28 that alter the mechanical characteristics of the retinal prosthesis (1) an increase in metal to silicone carrier ratio, and (2) an increase in the number of wires in the leadwire cable. Hence, we determined it was critical to perform a preclinical passive chronic safety study to determine the surgical safety, stability, conformability, robustness, and biocompatibility of this upgraded 44-channel electrode array, prior to proceeding to clinical trial.…”

Development of an image biosensor based on an optogenetically engineered cell for visual prostheses

“…1,2 Thus, visual prostheses are viable rehabilitative and therapeutic options to substitute and eventually restore useful visual sensation by electrically stimulating the surviving neural cells in the visual system. [3][4][5][6] However, high-resolution visual perception, longterm biocompatibility and safety still remain the main technical challenges in the development of visual prostheses.…”

Epiretinal stimulation with local returns enhances selectivity at cellular resolution

“…Several approaches have been proposed. For example, current steering, which involves passing current through several electrodes simultaneously in customized patterns, has been used in a range of neural structures from the cochlea (Townshend and White, 1987;Firszt et al, 2007) to deep brain nuclei (Martens et al, 2011) to the retina (Jepson et al, 2013;Matteucci et al, 2013;Dumm et al, 2014; see Bareket et al, 2017). Similarly, the use of local returns (rather than distant returns) to limit current spread without customization has been investigated using subretinal stimulation (Palanker et al, 2005;Palanker, 2014;Habib et al, 2013;Flores et al, 2016), suprachoroidal stimulation (Wong et al, 2009;Cicione et al, 2012;Sinclair et al, 2016), epiretinal stimulation , non-biological experiments (Dommel et al, 2005), and simulations (Joarder et al, 2011).…”