Interim Results from the International Trial of Second Sight's Visual Prosthesis

Doheny Eye Institute, University of Southern California, Los Angeles, California, USA.
Ophthalmology (Impact Factor: 6.14). 01/2012; 119(4):779-88. DOI: 10.1016/j.ophtha.2011.09.028
Source: PubMed


This study evaluated the Argus II Retinal Prosthesis System (Second Sight Medical Products, Inc., Sylmar, CA) in blind subjects with severe outer retinal degeneration.
Single-arm, prospective, multicenter clinical trial.
Thirty subjects were enrolled in the United States and Europe between June 6, 2007, and August 11, 2009. All subjects were followed up for a minimum of 6 months and up to 2.7 years.
The electronic stimulator and antenna of the implant were sutured onto the sclera using an encircling silicone band. Next, a pars plana vitrectomy was performed, and the electrode array and cable were introduced into the eye via a pars plana sclerotomy. The microelectrode array then was tacked to the epiretinal surface.
The primary safety end points for the trial were the number, severity, and relation of adverse events. Principal performance end points were assessments of visual function as well as performance on orientation and mobility tasks.
Subjects performed statistically better with the system on versus off in the following tasks: object localization (96% of subjects), motion discrimination (57%), and discrimination of oriented gratings (23%). The best recorded visual acuity to date is 20/1260. Subjects' mean performance on orientation and mobility tasks was significantly better when the system was on versus off. Seventy percent of the patients did not have any serious adverse events (SAEs). The most common SAE reported was either conjunctival erosion or dehiscence over the extraocular implant and was treated successfully in all subjects except in one, who required explantation of the device without further complications.
The long-term safety results of Second Sight's retinal prosthesis system are acceptable, and most subjects with profound visual loss perform better on visual tasks with system than without it.

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    • "First we argue that crowding and possibly masking by background clutter are applicable and relevant mostly to natural object recognition in a natural environment, though clearly letters can be crowded as can the direction of Gabor patches. However, the nature of visual acuity, contrast sensitivity, and object discrimination testing as performed with vision prostheses renders the stimuli free of the crowding effect (Humayun et al., 2012; Nau, Bach, & Fisher, 2013; Zrenner et al., 2011), which is the focus of our approach and proposed solution. Second, we argue that multiple choice testing, while a perfectly good method for measuring the threshold performance of the human or animal visual systems, is not sufficient to prove that prosthetic vision can deliver object recognition. "
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    • "Electrical stimulation of the retina enables introduction of information into the visual system of patients blinded by retinal degeneration , thereby restoring light sensitivity and, to a limited extent, some visually guided behavior (Humayun, 2009; Humayun et al., 2012; Wilke et al., 2011; Zrenner, 2013; Zrenner et al., 2010). However , systems currently approved for human use offer poor spatial resolution (typically below 20/1200) and include an extra-ocular power supply wired to the retinal implant, which requires very complex surgery with considerable risk of serious adverse events (Humayun et al., 2012; Zrenner et al., 2010). "
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    ABSTRACT: Loss of photoreceptors during retinal degeneration leads to blindness, but information can be reintroduced into the visual system using electrical stimulation of the remaining retinal neurons. Subretinal photovoltaic arrays convert pulsed illumination into pulsed electric current to stimulate the inner retinal neurons. Since required irradiance exceeds the natural luminance levels, an invisible near-infrared (915nm) light is used to avoid photophobic effects. We characterized the thresholds and dynamic range of cortical responses to prosthetic stimulation with arrays of various pixel sizes and with different number of photodiodes. Stimulation thresholds for devices with 140μm pixels were approximately half those of 70μm pixels, and with both pixel sizes, thresholds were lower with 2 diodes than with 3 diodes per pixel. In all cases these thresholds were more than two orders of magnitude below the ocular safety limit. At high stimulation frequencies (>20Hz), the cortical response exhibited flicker fusion. Over one order of magnitude of dynamic range could be achieved by varying either pulse duration or irradiance. However, contrast sensitivity was very limited. Cortical responses could be detected even with only a few illuminated pixels. Finally, we demonstrate that recording of the corneal electric potential in response to patterned illumination of the subretinal arrays allows monitoring the current produced by each pixel, and thereby assessing the changes in the implant performance over time.
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    • "o different types of retinal cells / retinal connections and different retinal implants rely on different retinal residual functioning ( e . g . , subretinal implants positioned in the outer surface of the retina or epiretinal implants positioned in the inner surface of the retina ; see for instance Djilas et al . , 2011 ; Zrenner et al . , 2011 ; Humayun et al . , 2012 ; Wang et al . , 2012 ) . This in turn creates an additional dif - ficulty for the stabilization of a unified approach for visual restoration , as each developing technique is only suited to the recovery of specific types of blindness and not for oth - ers . However , given the fast advances in biotechnological methods , retinal prosthe"
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