Advances in visual prostheses: engineering and biological challenges

In the paper

“Indeed, researchers demonstrated that visual perception and performance in solving visual tasks could improve with learning and time [20,98].”

What the sources say

• Partly supported

  The Introduction (Fig. 1 caption; no page number in our copy) says neural plasticity can improve perceptions of prosthetic vision and that learning and rehabilitation will help. The “Delivering of information to implants” section reports enhanced performance in a non-human primate model, but attributes it to eye movements. The paper does not report a demonstrated improvement in visual-task performance with learning over time. (LLM, conf=0.82)

  cites [20] Fernandez, 2018, Development of visual neuroprostheses: trends and challenges, Bioelectron. Med. sourceExperimental — accuracy not yet measured
• Partly supported

  The Discussion’s ‘Quantitative comparison with previous studies’ section says participants can learn to associate phosphene patterns with letters, supporting a role for learning in a specific visual-recognition task. It does not report that visual perception or task performance improved over time. The Discussion instead says participants immediately identified forms produced by dynamic stimulation without training. (LLM, conf=0.77)

  cites [98] Beauchamp, 2020, Dynamic stimulation of visual cortex produces form vision in sighted and blind humans, Cell sourceExperimental — accuracy not yet measured

In the paper

“So far, there have been very few preclinical studies in animals conducted to test the stimulation efficacy [81,83,84].”

What the sources say

• Supported

  The Abstract describes an experiment in alert monkeys testing whether LGN electrical stimulation creates visual percepts. The Results report 56 experiments in two adult monkeys, so this paper is an example of the animal studies cited in the sentence. (LLM, conf=0.88)

  cites [81] Pezaris, 2007, Demonstration of artificial visual percepts generated through thalamic microstimulation, Proc. Natl Acad. Sci. source
• Supported

  The paper says relatively little is known about LGB stimulation because surgical access is difficult. Its Materials and Methods describe a pig experiment investigating the feasibility of electrical stimulation for a visual prosthesis, and the introductory passage identifies a prior monkey study. Together, these support the broad statement that animal studies testing this approach have been scarce. (LLM, conf=0.84)

  cites [83] Choi, 2014, Lateral geniculate body evoked potentials elicited by visual and electrical stimulation, Korean J. Ophthalmol. source
• Not checked yetcites [84] Tangutooru, 2014, Early design considerations for a thalamic visual prosthesis to treat blindness resulting from glaucoma source

In the paper

“A cortical prosthesis offers the advantage of artificial vision in most conditions of blindness, excluding traumatic brain injuries and stroke [7].”

What the sources say

• Partly supported

  The Visual cortex section says cortical prostheses are applicable to all forms of blindness other than cortical injury or stroke. This supports the broad applicability and stroke exception, but the claim replaces the paper’s narrower exception of cortical injury with traumatic brain injury, which the passage does not equate with cortical injury. (LLM, conf=0.86)

  cites [7] Mirochnik, 2019, Contemporary approaches to visual prostheses, Mil. Med. Res. sourceExperimental — accuracy not yet measured

In the paper

“Recently, the safety and biocompatibility of graphene electrodes for retinal implants has been assessed [172].”

What the sources say

• Supported

  The Introduction describes an in vivo assessment of graphene implant biocompatibility in rat retinas. The Discussion reports monitoring implant stability and checking for abnormalities such as edema and hemorrhage. The claim says these properties were assessed, not that functional electrodes were proven safe. (LLM, conf=0.92)

  cites [172] Nguyen, 2021, Novel graphene electrode for retinal implants: an in vivo biocompatibility study, Front. Neurosci. source

In the paper

“In animal studies, researchers have found that stimulation activates interconnected neurons distant from the electrode, even at low currents [145].”

What the sources say

• Partly supported

  The Discussion reports that near-threshold stimulation activates a sparse, widely distributed set of neuronal cell bodies, including cells distant from the electrode. It does not establish that those distant cells are interconnected; its discussion of activation in connected partners is an inference and describes only a small number of spikes. (LLM, conf=0.85)

  cites [145] Histed, 2009, Direct activation of sparse, distributed populations of cortical neurons by electrical microstimulation, Neuron sourceExperimental — accuracy not yet measured

In the paper

“Photovoltaic retinal prostheses [48] were the first example of neurostimulation devices providing fully wireless electrical stimulation to the nervous system without the need for implantable batteries or active electronic units.”

What the sources say

• Partly supported

  The Introduction’s PRIMA system section describes a wireless prosthesis whose photovoltaic pixels convert projected light into current that stimulates retinal neurons. It does not establish that photovoltaic retinal prostheses were the first neurostimulation devices to do this, or explicitly state that the implant has no battery or active electronic units. Page numbers are unavailable in our copy. (LLM, conf=0.84)

  cites [48] Palanker, 2020, Photovoltaic restoration of central vision in atrophic age-related macular degeneration, Ophthalmology sourceExperimental — accuracy not yet measured

In the paper

“Therefore, they can offer artificial vision only to blind patients with outer retinal diseases, causing the progressive loss of retinal photoreceptors.”

In the paper

“Visual prostheses bypass the damaged segment of the visual path and electrically stimulate the downstream surviving visual neurons to induce artificial vision.”

In the paper

“The device position (epiretinal, subretinal or suprachoroidal) and the characteristics of the electrical pulses (such as duration and waveform) determine which cell population is predominantly activated [28,29].”

What the sources say

• Not checked yetcites [28] Boinagrov, 2014, Selectivity of direct and network-mediated stimulation of the retinal ganglion cells with epi-, sub- and intraretinal electrodes, J. Neural Eng. source
• Not checked yetcites [29] Chenais, 2019, Capacitive-like photovoltaic epiretinal stimulation enhances and narrows the network-mediated activity of retinal ganglion cells by recruiting the lateral inhibitory network, J. Neural Eng. source

In the paper

“With multiple devices granted Food and Drug Administration (FDA) approval and CE mark for clinical use and many others in preclinical and clinical validation, visual prostheses represent a viable therapeutic solution to improve mobility and daily-life activities in blind individuals.”

In the paper

“However, the network-mediated stimulation is also possible from an epiretinal device if long (more than 8 ms) or non-rectangular pulses are used [29][30][31].”

What the sources say

• Not checked yetcites [29][30][31]

In the paper

“Although clinical trials showed that vision restoration is still far away, significant technological advances make visual prostheses a valuable solution for blind patients.”

In the paper

“Epiretinal surgery allows the placement of sizable devices for artificial vision in a large portion of the visual field [38][39][40].”

What the sources say

• Not checked yetcites [38][39][40]

In the paper

“Today, the synergistic convergence of science and technology holds the potential to provide blind patients with artificial vision using visual prostheses: a type of implantable medical device able to reactivate visual neurons using electrical stimulation.”

In the paper

“Besides the ease of surgical accessibility, they can also profit from the retinotopic organisation and early positioning in the visual pathway [26,27].”

What the sources say

• Not checked yetcites [26] Farnum, 2020, New vision for visual prostheses front neurosci-switz, Front. Neurosci. source
• Not checked yetcites [27] Ghezzi, 2015, Retinal prostheses: progress toward the next generation implants, Front. Neurosci. source

In the paper

“Wide artificial vision is crucial for totally blind people to perform everyday visual tasks such as general orientation, safe ambulation, obstacle avoidance and object recognition [41].”

What the sources say

• Not checked yetcites [41] Thorn, 2020, Virtual reality simulation of epiretinal stimulation highlights the relevance of the visual angle in prosthetic vision, J. Neural Eng. source

In the paper

“Epiretinal prostheses with short (e.g. less than 1 ms) and rectangular pulses directly activate RGCs.”

In the paper

“The presence of choroid, RPE, and debris of photoreceptors makes the selective stimulation of BCs extremely difficult, leading to poor spatial resolution [59,60].”

What the sources say

• Not checked yetcites [59] Petoe, 2017, Determining the contribution of retinotopic discrimination to localization performance with a suprachoroidal retinal prosthesis, Investigative Opthalmol. Vis. Sci. source
• Not checked yetcites [60] Shivdasani, 2017, Identification of characters and localization of images using direct multiple-electrode stimulation with a suprachoroidal retinal prosthesis, Investigative Ophthalmol. Vis. Sci. source

In the paper

“First, it can help patients who lost the optic nerve, for example, due to glaucoma or ocular trauma.”

In the paper

“The lack of stable phosphene could be attributed to the lack of mechanical stability of the cuff device [68].”

What the sources say

• Not checked yetcites [68] 2014, Chapter 1—restoring vision to the blind: the new age of implanted visual prostheses, Transl. Vis. Sci. Technol. source

In the paper

“A major constraint in subretinal prostheses however is the maximum size of the implant, which is limited by the risk of retinal detachment.”

In the paper

“Due to axonal activation, phosphenes often appear with an elongated shape distorting the image perceived by the patient [46].”

What the sources say

• Not checked yetcites [46] Humayun, 2003, Visual perception in a blind subject with a chronic microelectronic retinal prosthesis, Vis. Res. source

In the paper

“This location reduces the risk of retinal damage compared to the other two approaches since it does not require intravitreal manipulation [54].”

What the sources say

• Not checked yetcites [54] Villalobos, 2013, A wide-field suprachoroidal retinal prosthesis is stable and well tolerated following chronic implantation, Investigative Ophthalmol. Vis. Sci. source

In the paper

“For totally blind patients, like in RP or severe forms of AMD, a much wider visual field would be required to allow the patient to perform everyday tasks [41].”

What the sources say

• Not checked yetcites [41] Thorn, 2020, Virtual reality simulation of epiretinal stimulation highlights the relevance of the visual angle in prosthetic vision, J. Neural Eng. source

In the paper

“The C-Sight project tested an optic nerve prosthesis based on four stiff electrodes to stimulate the intra-orbital segment of the nerve in rabbits and cats [71][72][73].”

What the sources say

• Not checked yetcites [71][72][73]

In the paper

“Therefore, intraneural arrays were implemented to increase fibre selectivity (figure 6(a)).”

In the paper

“Moreover, another advantage of epiretinal implants is the facilitation of heat dissipation via the vitreous [42].”

What the sources say

• Not checked yetcites [42] Opie, 2012, Heating of the eye by a retinal prosthesis: modeling, cadaver and in vivo study, IEEE Trans. Biomed. Eng. source

In the paper

“The main surgical drawback is the requirement of one or more retinal tacks to anchor the prosthesis to the retina, which could cause retinal damage.”

In the paper

“The other challenge presented by existing cuff devices is to selectively activate specific fibres, including those in the central portion of the nerve, to improve the resolution of artificial vision [69].”

What the sources say

• Not checked yetcites [69] Fried, 2020, Selective activation of the visual cortex, Nat. Biomed. Eng. source

In the paper

“However, a high risk of subretinal and suprachoroidal haemorrhage has been reported during preclinical and clinical evaluation [55][56][57].”

What the sources say

• Not checked yetcites [55][56][57]

In the paper

“Today, only one subretinal prosthesis, the Alpha IMS implant (figure 5(b)) and its successor Alpha AMS (Retina Implant AG), have received marketing approval (CE mark) [52,53].”

What the sources say

• Not checked yetcites [52] Zrenner, 2011, Subretinal electronic chips allow blind patients to read letters and combine them to words, Proc. R. Soc. B source
• Not checked yetcites [53] Edwards, 2018, Assessment of the electronic retinal implant alpha AMS in restoring vision to blind patients with end-stage retinitis pigmentosa, Ophthalmology source

In the paper

“On the other hand, subretinal surgery is more delicate due to the adhesive junctions between the retina and the RPE [47].”

What the sources say

• Not checked yetcites [47] Mills, 2017, Electronic retinal implants and artificial vision: journey and present, Eye source

In the paper

“Three platinum wires were implanted in the optic disc of an RP patient eliciting phosphenes in three distinct positions for each electrode [70].”

What the sources say

• Not checked yetcites [70] Sakaguchi, 2009, Artificial vision by direct optic nerve electrode (AV-DONE) implantation in a blind patient with retinitis pigmentosa, J. Artif. Organs source

In the paper

“Results in rabbits showed that the selective activation of different portions of the optic nerve induced spatially organised cortical activation patterns in the rabbit's V1 [63,74,75].”

What the sources say

• Not checked yetcites [63] Gaillet, 2021, A machine-learning algorithm correctly classifies cortical evoked potentials from both visual stimulation and electrical stimulation of the optic nerve, J. Neural Eng. source
• Not checked yetcites [74] Gaillet, 2020, Spatially selective activation of the visual cortex via intraneural stimulation of the optic nerve, Nat. Biomed. Eng. source
• Not checked yetcites [75] Borda, 2022, Three-dimensional multilayer concentric bipolar electrodes restrict spatial activation in optic nerve stimulation, J. Neural Eng. source

In the paper

“The research proved that optic nerve stimulation elicits phosphenes in the entire visual field with some degree of selectivity.”

In the paper

“However, since the LGN is located after the optic chiasm, a bilateral implant is required to cover both hemifields.”

In the paper

“A way to mitigate this phenomenon is to use long and non-rectangular pulses that will preferentially induce network-mediated stimulation, resulting in a more localised activation [29,31].”

What the sources say

• Not checked yetcites [29] Chenais, 2019, Capacitive-like photovoltaic epiretinal stimulation enhances and narrows the network-mediated activity of retinal ganglion cells by recruiting the lateral inhibitory network, J. Neural Eng. source
• Not checked yetcites [31] Weitz, 2015, Improving the spatial resolution of epiretinal implants by increasing stimulus pulse duration, Sci. Transl. Med. source

In the paper

“The results showed excellent retinotopic correspondence between the quadrant of the visual field in which the phosphene appeared and the electrode used.”

In the paper

“Another group has validated a thin and flexible intraneural electrode array called OpticSELINE (figure 6(b)).”

In the paper

“Second, it is possible to cover a wide visual field with an overrepresentation of the foveal region, thus restoring possibly high-acuity artificial vision [79].”

What the sources say

• Not checked yetcites [79] Mullen, 2008, Color responses of the human lateral geniculate nucleus: selective amplification of S-cone signals between the lateral geniculate nucleno and primary visual cortex measured with high-field fMRI, Eur. J. Neurosci. source

In the paper

“In this case, phosphenes are evoked only in a few degrees of the visual field.”

In the paper

“However, artificial vision still does not offer the patient the possibility of regaining fully functional vision.”

In the paper

“However, the current amplitudes required to elicit a phosphene is much higher than with intracortical electrodes because of the distance between the electrodes and the neurons.”

In the paper

“Many studies have highlighted that restoring a large visual field is necessary to make artificial vision helpful in everyday life [41,[112][113][114][115][116].”

What the sources say

• Not checked yetcites [41,[112][113][114][115][116]

In the paper

“Therefore, it might encode a more naturalistic perception.”

In the paper

“Stimulation paradigms adapted explicitly for each patient might also be required [96].”

What the sources say

• Not checked yetcites [96] Maynard, 2001, Visual prostheses, Annu. Rev. Biomed. Eng. source

In the paper

“In 1968, Brindley and Lewin proposed the first permanently implanted cortical prosthesis, consisting of an epineural array of 80 electrodes implanted over the occipital cortex [89,90].”

What the sources say

• Not checked yetcites [89] Brindley, 1968, The sensations produced by electrical stimulation of the visual cortex, J. Physiol. source
• Not checked yetcites [90] Brindley, 1970, Sensations produced by electrical stimulation of the occipital poles of the cerebral hemispheres, and their use in constructing visual prostheses, Ann. R. Coll. Surg.

In the paper

“After the pioneering experiments of Löwenstein and Borchardt [16], Krause [17] and Foerster [18], cortical prostheses were the first ones to be developed among visual implants.”

What the sources say

• Not checked yetcites [16] Löwenstein, 1918, Symptomatologie und elektrische Reizung bei einer Schußverletzung des Hinterhauptlappens, Deutsch. Z. Nervenheilkunde source
• Not checked yetcites [17] Krause, 1924, Die Sehbahn in Chirurgischer Beziehung und die Faradische Reizung des Sehzentrums, Klin. Wochenschr. source
• Not checked yetcites [18] Foerster, 1929, Beitrage zur pathophysiologie der sehbahn und der spehsphare, J. Psychol. Neurol.

In the paper

“Contrary to epineural implants, intraneural electrodes cannot be placed in the interhemispheric fissure, where a large portion of the visual field is mapped [102].”

What the sources say

• Not checked yetcites [102] Schira, 2012, Brain mapping: the (un)folding of striate cortex, Curr. Biol. source

In the paper

“He recognised patterns induced by sequential activation of electrodes corresponding to the Braille alphabet [91].”

What the sources say

• Not checked yetcites [91] Donaldson, 1973, Experimental visual prosthesis, Proc. Inst. Electr. Eng. source

In the paper

“However, the implantation technique requires pneumatic insertion tools that limit the area reachable with the device to only the occipital pole.”

In the paper

“Therefore, placing the electrodes in higher visual areas where spatial representation is still preserved [26,103] could be a possible solution to enlarge the visual field.”

What the sources say

• Not checked yetcites [26] Farnum, 2020, New vision for visual prostheses front neurosci-switz, Front. Neurosci. source
• Not checked yetcites [103] Meikle, 2022, Neurophysiological considerations for visual implants, Brain Struct. Funct. source

In the paper

“On the other hand, the complexity of the visual cortex with neurons specifically tuned for specific cues [95] could hinder the ability to evoke simple uniformly shaped phosphenes.”

What the sources say

• Not checked yetcites [95] Fernandes, 2012, Artificial vision through neuronal stimulation, Neurosci. Lett. source

In the paper

“Visual prostheses have been an incredible breakthrough leading to artificial vision in several blind patients suffering from RP, AMD, glaucoma, or other traumatic injuries.”

In the paper

“One way to overcome this problem in retinal prostheses is to use wireless photovoltaic technology where each pixel converts incident light into electrical stimulation [38,39,48,49,[126][127][128][129][130][131][132].”

What the sources say

• Not checked yetcites [38,39,48,49,[126][127][128][129][130][131][132]

In the paper

“Clinical trials showed that the best visual resolution was achieved using subretinal prostheses.”

In the paper

“Another challenge threatening artificial vision lies in the capability of the device to stimulate multiple independent phosphenes to create form perception.”

In the paper

“Reducing the size of the electrode is necessary to increase electrode density.”

In the paper

“Grating acuities reported in the literature range from 20/1260 with the epiretinal Argus® II implant to 20/364 with the subretinal Alpha-AMS implant [53].”

What the sources say

• Not checked yetcites [53] Edwards, 2018, Assessment of the electronic retinal implant alpha AMS in restoring vision to blind patients with end-stage retinitis pigmentosa, Ophthalmology source

In the paper

“Therefore, as a rule of thumb, enlarging the visual field means having electrodes covering a wider tissue area.”

In the paper

“In retinal prostheses, wide coverage of the retina remains an open challenge.”

In the paper

“POLYRETINA is a high-density wide-field epiretinal prosthesis containing 10 498 photovoltaic pixels distributed over an active area of approximately 43 • [38,39,131,132].”

What the sources say

• Not checked yetcites [38] Ferlauto, 2018, Design and validation of a foldable and photovoltaic wide-field epiretinal prosthesis, Nat. Commun. source
• Not checked yetcites [39] Vagni, 2022, POLYRETINA restores light responses in vivo in blind Göttingen minipigs, Nat. Commun. source
• Not checked yetcites [131] Leccardi, 2020, Photovoltaic organic interface for neuronal stimulation in the near-infrared, Commun. Mater. source
• Not checked yetcites [132] Chenais, 2021, Photovoltaic retinal prosthesis restores high-resolution responses to single-pixel stimulation in blind retinas, Commun. Mater. source

In the paper

“A similar effect has also been observed with suprachoroidal implants, where the subjects described geometrically complex percepts [141].”

What the sources say

• Not checked yetcites [141] Sinclair, 2016, The appearance of phosphenes elicited using a suprachoroidal retinal prosthesis phosphenes of a suprachoroidal retinal prosthesis, Investigative Ophthalmol. Vis. Sci. source

In the paper

“However, this number might underestimate the real needs of implanted patients due to the perceptual and behavioural learning required to adapt to artificial vision [121,122].”

What the sources say

• Not checked yetcites [121] Beyeler, 2017, Learning to see again: biological constraints on cortical plasticity and the implications for sight restoration technologies, J. Neural Eng. source
• Not checked yetcites [122] Chen, 2009, Simulating prosthetic vision: II. Measuring functional capacity, Vis. Res. source

In the paper

“Moreover, it is possible only for epiretinal and suprachoroidal implants.”

In the paper

“Nevertheless, the main issue with wider prostheses is the limited number of electrodes usually available in the array.”

In the paper

“An epiretinal implant like POLYRETINA on the other hand can have more than 10 000 electrodes over 43 • (approximately 140 mm 2 ), that is an area ten times larger than the total cross-area of the optic nerve.”

In the paper

“Studies under simulated prosthetic vision identified a visual angle of 30 • -35 • as the minimal requirement for mobility and daily tasks (figure 7) [41,[117][118][119][120].”

What the sources say

• Not checked yetcites [41,[117][118][119][120]

In the paper

“This comparison shows that subretinal prostheses have so far provided better resolution than epiretinal prostheses.”

In the paper

“However, their small size is a challenge for implant and electrode miniaturisation, particularly when targeting the optic nerve.”

In the paper

“POLYRETINA reported ex-vivo a spatial resolution of 120 µm (or 20/480) equivalent to the electrode separation [132].”

What the sources say

• Not checked yetcites [132] Chenais, 2021, Photovoltaic retinal prosthesis restores high-resolution responses to single-pixel stimulation in blind retinas, Commun. Mater. source

In the paper

“Sinusoidal electrical stimuli in epiretinal configuration allowed the classification of overlapping but spatially displaced objects in explanted retinas [139].”

What the sources say

• Not checked yetcites [139] Corna, 2021, Discrimination of simple objects decoded from the output of retinal ganglion cells upon sinusoidal electrical stimulation, J. Neural Eng. source

In the paper

“In conventional visual prostheses, the electrode number and electrode density are limited by the implantable pulse generator, the cable from the pulse generator to the array, and the feedlines in the array.”

In the paper

“Multiple PRIMA devices have been placed in the rabbit eye to increase the visual angle [123].”

What the sources say

• Not checked yetcites [123] Lee, 2016, Implantation of modular photovoltaic subretinal prosthesis, Ophthalmic Surg. Lasers Imaging Retin. source

In the paper

“However, patients might still experience arcuate and linear phosphenes when high current amplitudes are used [140], most probably due to direct RGC activation.”

What the sources say

• Not checked yetcites [140] Wilke, 2011, Spatial resolution and perception of patterns mediated by a subretinal 16-electrode array in patients blinded by hereditary retinal dystrophies, Investigative Opthalmol. Vis. Sci. source

In the paper

“Also, high stimulation frequency allows discrimination among RGC types [138].”

What the sources say

• Not checked yetcites [138] Cai, 2013, The response of retinal neurons to high-frequency stimulation, J. Neural Eng. source

In the paper

“Despite these results, the selective activation of a few optic nerve fibres by each electrode remains an open challenge.”

In the paper

“A common approach is to use bipolar stimulation through two close electrodes, as shown in retinal [36,143,144], optic nerve [75], and thalamic prostheses [81].”

What the sources say

• Not checked yetcites [36] Tong, 2020, Stimulation strategies for improving the resolution of retinal prostheses, Front. Neurosci. source
• Not checked yetcites [143] Ho, 2019, Characteristics of prosthetic vision in rats with subretinal flat and pillar electrode arrays, J. Neural Eng. source
• Not checked yetcites [144] Shivdasani, 2014, Factors affecting perceptual thresholds in a suprachoroidal retinal prosthesis factors affecting retinal prosthesis thresholds, Investigative Ophthalmol. Vis. Sci. source
• Not checked yetcites [75] Borda, 2022, Three-dimensional multilayer concentric bipolar electrodes restrict spatial activation in optic nerve stimulation, J. Neural Eng. source
• Not checked yetcites [81] Pezaris, 2007, Demonstration of artificial visual percepts generated through thalamic microstimulation, Proc. Natl Acad. Sci. source

In the paper

“In sighted humans, the Troxler effect is prevented by various ocular micromovements (tremors, drifts and microsaccades) that refresh a static image and limit retinal adaptation [151,152].”

What the sources say

• Not checked yetcites [151] Greschner, 2002, Retinal ganglion cell synchronization by fixational eye movements improves feature estimation, Nat. Neurosci. source
• Not checked yetcites [152] Kagan, 2008, Saccades and drifts differentially modulate neuronal activity in V1: effects of retinal image motion, position, and extraretinal influences, J. Vis. source

In the paper

“A significant limitation in artificial vision is phosphene fading [148][149][150]”

What the sources say

• Not checked yetcites [148] Fornos, 2012, Temporal properties of visual perception on electrical stimulation of the retina, Investigative Opthalmol. Vis. Sci. source
• Not checked yetcites [149] Stronks, 2014, The functional performance of the Argus II retinal prosthesis, Expert Rev. Med. Device source
• Not checked yetcites [150] Stingl, 2013, Artificial vision with wirelessly powered subretinal electronic implant alpha-IMS, Proc. R. Soc. B source

In the paper

“On the other hand, the denser the electrodes, the higher is the risk of cross-talk between electrodes.”

In the paper

“However, traditional computer vision approaches, such as edge detection, contrast enhancement, and difference of Gaussians, have been tested in retinal prostheses and proved limited usefulness in daily life [181][182][183].”

What the sources say

• Not checked yetcites [181] Humayun, 2009, Preliminary 6 month results from the argustm ii epiretinal prosthesis feasibility study source
• Not checked yetcites [182] Shire, 2012, ASIC design and data communications for the Boston retinal prosthesis
• Not checked yetcites [183] Barnes, 2016, Vision function testing for a suprachoroidal retinal prosthesis: effects of image filtering, J. Neural Eng. source

In the paper

“So far, flicker fusion has been achieved only for the PRIMA device in AMD patients [48].”

What the sources say

• Not checked yetcites [48] Palanker, 2020, Photovoltaic restoration of central vision in atrophic age-related macular degeneration, Ophthalmology source

In the paper

“Different groups demonstrated that spatially organised phosphenes are induced by applying current-steering or modulating current amplitudes during optic nerve stimulation [65,73].”

What the sources say

• Not checked yetcites [65] Veraart, 2003, Pattern recognition with the optic nerve visual prosthesis, Artif. Organs source
• Not checked yetcites [73] Yan, 2016, Electrically evoked responses in the rabbit cortex induced by current steering with penetrating optic nerve electrodes, Investigative Ophthalmol. Vis. Sci. source

In the paper

“Generally, short trains of charge-balanced biphasic pulses evoke individual phosphenes [146].”

What the sources say

• Not checked yetcites [146] Cicione, 2014, Spatiotemporal interactions in the visual cortex following paired electrical stimulation of the retina, Investigative Ophthalmol. Vis. Sci. source

In the paper

“Retinal prostheses can avoid fading if three criteria are met [153].”

What the sources say

• Not checked yetcites [153] Thorn, 2022, Virtual reality validation of naturalistic modulation strategies to counteract fading in retinal stimulation, J. Neural Eng. source

In the paper

“Stimulation approaches, such as dynamic current steering, have been investigated and proved to be a helpful strategy for recognising shapes [91,98]”

What the sources say

• Not checked yetcites [91] Donaldson, 1973, Experimental visual prosthesis, Proc. Inst. Electr. Eng. source
• Not checked yetcites [98] Beauchamp, 2020, Dynamic stimulation of visual cortex produces form vision in sighted and blind humans, Cell source

In the paper

“The electrode-tissue interface is one of the most critical elements of a neural interface from a mechanical, chemical and electrical point of view [158,159].”

What the sources say

• Not checked yetcites [158] Woeppel, 2017, Recent advances in neural electrode–tissue interfaces, Curr. Opin. Biomed. Eng. source
• Not checked yetcites [159] Leccardi, 2020, Organic electronics for neuroprosthetics, Healthc. Technol. Lett. source

In the paper

“The sequential activation of electrodes is an attractive strategy allowing form vision in patients [91,98].”

What the sources say

• Not checked yetcites [91] Donaldson, 1973, Experimental visual prosthesis, Proc. Inst. Electr. Eng. source
• Not checked yetcites [98] Beauchamp, 2020, Dynamic stimulation of visual cortex produces form vision in sighted and blind humans, Cell source

In the paper

“Among carbon-based materials, graphene-based materials emerge in neural interfaces, given their outstanding electrical and optical properties [171].”

What the sources say

• Not checked yetcites [171] Kostarelos, 2017, Graphene in the design and engineering of next‐generation neural interfaces, Adv. Mater. source

In the paper

“Machine learning approaches, such as convolutional neural networks [189] and deep learning [190,191], could recognise multiple objects in complex scenes, helping navigation, obstacle avoidance and target object finding.”

What the sources say

• Not checked yetcites [189] Sanchez-Garcia, 2019, Indoor scenes understanding for visual prosthesis with fully convolutional networks source
• Not checked yetcites [190] Lozano, 2020, Neurolight: a deep learning neural interface for cortical visual prostheses, Int. J. Neural Syst. source
• Not checked yetcites [191] van Steveninck, 2022, End-to-end optimization of prosthetic vision, J. Vis. source

In the paper

“Among the approaches under investigation, inductive power transfer seems to be the preferred solution for high-resolution intra-cortical stimulation [202] due to the small distance between the transmitter and the receiver.”

What the sources say

• Not checked yetcites [202] Wong, 2019, CMOS stimulating chips capable of wirelessly driving 473 electrodes for a cortical vision prosthesis, J. Neural Eng. source

In the paper

“These rodents show a significant remodelling of the retinal circuits after photoreceptor degeneration [207].”

What the sources say

• Not checked yetcites [207] Jones, 2003, Retinal remodeling triggered by photoreceptor degenerations, J. Comp. Neurol. source

In the paper

“In particular, new developments in organic bioelectronics and photovoltaics showed superior features in conformability, flexibility and stretchability [38,39] compared to silicon-based technology.”

What the sources say

• Not checked yetcites [38] Ferlauto, 2018, Design and validation of a foldable and photovoltaic wide-field epiretinal prosthesis, Nat. Commun. source
• Not checked yetcites [39] Vagni, 2022, POLYRETINA restores light responses in vivo in blind Göttingen minipigs, Nat. Commun. source

In the paper

“Given the unpredictable nature of these plastic events, if stimulation parameters are not adapted accordingly, they might distort evoked phosphenes.”

In the paper

“Although remarkable engineering progress has been made since the very first prototype of a visual prosthesis [87], results from the clinical use of commercially available retinal prostheses showed that for now, patients affected by retinal degeneration could only expect a form of vision substitution (artificial vision) rather than vision restoration [221].”

What the sources say

• Not checked yetcites [221] Erickson-Davis, 2021, What do blind people ‘see’ with retinal prostheses? Observations and qualitative reports of epiretinal implant users, PLoS One source

In the paper

“Preclinical trials are performed either on sighted [74,100,[204][205][206] or blind [126,132] animal models.”

What the sources say

• Not checked yetcites [74] Gaillet, 2020, Spatially selective activation of the visual cortex via intraneural stimulation of the optic nerve, Nat. Biomed. Eng. source
• Not checked yetcites [100] Chen, 2020, Shape perception via a high-channel-count neuroprosthesis in monkey visual cortex, Science source
• Not checked yetcites [204] Majji, 1999, Long-term histological and electrophysiological results of an inactive epiretinal electrode array implantation in dogs, Investigative Ophthalmol. Vis. Sci.

In the paper

“Additional criteria should be considered since these tests are not informative on the functional preservation of the retinal circuits.”

In the paper

“The success of visual prostheses strongly depends on our understanding of the adaptive and compensatory changes occurring within the brain [220] and the role of perceptual learning.”

What the sources say

• Not checked yetcites [220] Merabet, 2007, ‘Who is the ideal candidate?’: decisions and issues relating to visual neuroprosthesis development, patient testing and neuroplasticity, J. Neural Eng. source

In the paper

“Moreover, cables and connectors apply mechanical forces on the implant and the tissue, causing long-term scarring [201].”

What the sources say

• Not checked yetcites [201] Barbruni, 2020, Miniaturised wireless power transfer systems for neurostimulation: a review, IEEE Trans. Biomed. Circuits Syst. source

In the paper

“One of the first permanent cortical stimulators implanted in humans was a visual prosthesis [89].”

What the sources say

• Not checked yetcites [89] Brindley, 1968, The sensations produced by electrical stimulation of the visual cortex, J. Physiol. source

In the paper

“However, due to the complexity of saliency calculation, real-time performance is the limiting factor for visual prostheses [185][186][187][188].”

What the sources say

• Not checked yetcites [185] Li, 2018, Image processing strategies based on saliency segmentation for object recognition under simulated prosthetic vision, Artif. Intell. Med. source
• Not checked yetcites [186] Li, 2017, A real-time image optimization strategy based on global saliency detection for artificial retinal prostheses, Inf. Sci. source
• Not checked yetcites [187] Guo, 2018, Optimization of visual information presentation for visual prosthesis, Int. J. Biomed. Imaging source

In the paper

“The GENNARIS system (Monash Vision Group) uses inductive power transfer from a single transmitter coil to transmit data and power to 11 implanted receiver with 43 electrodes each [106].”

What the sources say

• Not checked yetcites [106] Rosenfeld, 2020, Tissue response to a chronically implantable wireless intracortical visual prosthesis (Gennaris array), J. Neural Eng. source

In the paper

“A patient implanted with the Argus® II estimated that the total cost of device, surgery and rehabilitation was 497 000 USD [228].”

What the sources say

• Not checked yetcites [228] Strickland, 2022, What happens when a bionic body part becomes obsolete?, IEEE Spectr. source

In the paper

“Additionally, the cognitive fatigue reported so far by users has discouraged them from using the implant long-term [221].”

What the sources say

• Not checked yetcites [221] Erickson-Davis, 2021, What do blind people ‘see’ with retinal prostheses? Observations and qualitative reports of epiretinal implant users, PLoS One source

In the paper

“The Argus® II [111] was among the first implantable microelectrode arrays manufactured with cleanroom processes to be approved by regulatory agencies.”

What the sources say

• Not checked yetcites [111] Luo, 2016, The Argus® II retinal prosthesis system, Prog. Retin. Eye Res. source

In the paper

“The subretinal visual implant Alpha IMS [150] was one of the first CE-approved implantable medical devices with a high-channel-count (1500 pixels) and implantable electronics in contact with the central nervous system.”

What the sources say

• Not checked yetcites [150] Stingl, 2013, Artificial vision with wirelessly powered subretinal electronic implant alpha-IMS, Proc. R. Soc. B source

In the paper

“Another significant limiting factor for better artificial vision is the insufficient understanding of the neural visual code in blind individuals and the effect of visual deprivation and plasticity [203].”

What the sources say

• Not checked yetcites [203] Merabet, 2005, What blindness can tell us about seeing again: merging neuroplasticity and neuroprostheses, Nat. Rev. Neurosci. source

In the paper

“They affect the spatial localisation of the phosphene elicited by retinal [200] and cortical [101] stimulation, even after years of blindness.”

What the sources say

• Not checked yetcites [200] Caspi, 2017, Retinotopic to spatiotopic mapping in blind patients implanted with the Argus II retinal prosthesis spatial mapping in a visual prosthesis, Investigative Ophthalmol. Vis. Sci. source
• Not checked yetcites [101] Caspi, 2021, Eye movements and the perceived location of phosphenes generated by intracranial primary visual cortex stimulation in the blind, Brain Stimul. source