An update on retinal prostheses

Ayton, Lauren N; Barnes, Nick; Dagnelie, Gislin; Fujikado, Takashi; Goetz, Georges; Hornig, R.; Jones, Bryan W.; Muqit, Mahiul M. K.; Rathbun, Daniel L.; Štingl, Katarína; Weiland, James D.; Petoe, Matthew A.

doi:10.1016/j.clinph.2019.11.029

Cited by 130 publications

(143 citation statements)

References 111 publications

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“…Retinal implants with the features described in this work are composed of a few thousand (~7000) photodiodes in the interest areas, each representing a pixel ( Figure 7 ). The clinical results from retinal prostheses have been reviewed recently [ 65 ]. Nevertheless, the visual resolution obtained from existing devices is very limited, meaning that even recognizing simple objects is challenging.…”

Section: Discussionmentioning

confidence: 99%

Human Eye Optics within a Non-Euclidian Geometrical Approach and Some Implications in Vision Prosthetics Design

et al. 2021

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An analogy with our previously published theory on the ionospheric auroral gyroscope provides a new perspective in human eye optics. Based on cone cells’ real distribution, we model the human eye macula as a pseudospherical surface. This allows the rigorous description of the photoreceptor cell densities in the parafoveal zones modeled further by an optimized paving method. The hexagonal photoreceptors’ distribution has been optimally projected on the elliptical pseudosphere, thus designing a prosthetic array counting almost 7000 pixel points. Thanks to the high morphological similarities to a normal human retina, the visual prosthesis performance in camera-free systems might be significantly improved.

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Section: Discussionmentioning

confidence: 99%

Human Eye Optics within a Non-Euclidian Geometrical Approach and Some Implications in Vision Prosthetics Design

et al. 2021

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“…Two larger diameter (2 mm) electrodes were reserved as return electrodes and 44 smaller electrodes (1 mm diameter) were available for stimulation. 23 The infrared ocular images (Spectralis, Heidelberg Engineering Gmbh, Germany) presented in Figure 1 show the placement of the array with respect to the fovea for each subject.…”

Section: Methodsmentioning

confidence: 99%

Oculomotor Responses to Dynamic Stimuli in a 44-Channel Suprachoroidal Retinal Prosthesis

Titchener

Kvansakul

Shivdasani

et al. 2020

Trans. Vis. Sci. Tech.

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Purpose To investigate oculomotor behavior in response to dynamic stimuli in retinal implant recipients. Methods Three suprachoroidal retinal implant recipients performed a four-alternative forced-choice motion discrimination task over six sessions longitudinally. Stimuli were a single white bar (“moving bar”) or a series of white bars (“moving grating”) sweeping left, right, up, or down across a 42″ monitor. Performance was compared with normal video processing and scrambled video processing (randomized image-to-electrode mapping to disrupt spatiotemporal structure). Eye and head movement was monitored throughout the task. Results Two subjects had diminished performance with scrambling, suggesting retinotopic discrimination was used in the normal condition and made smooth pursuit eye movements congruent to the moving bar stimulus direction. These two subjects also made stimulus-related eye movements resembling optokinetic reflex (OKR) for moving grating stimuli, but the movement was incongruent with stimulus direction. The third subject was less adept at the task, appeared primarily reliant on head position cues (head movements were congruent to stimulus direction), and did not exhibit retinotopic discrimination and associated eye movements. Conclusions Our observation of smooth pursuit indicates residual functionality of cortical direction-selective circuits and implies a more naturalistic perception of motion than expected. A distorted OKR implies improper functionality of retinal direction-selective circuits, possibly due to retinal remodeling or the non-selective nature of the electrical stimulation. Translational Relevance Retinal implant users can make naturalistic eye movements in response to moving stimuli, highlighting the potential for eye tracker feedback to improve perceptual localization and image stabilization in camera-based visual prostheses.

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“…However, in those with endstage disease photoreceptor replacement methods are required. Photoreceptor replacement could be achieved by injection of progenitor cells into the subretinal space, [37][38][39] surgical implantation of electronic implants 40 or genetically inducing expression of bacterial opsins in neurons of the inner retina using optogenetics. 41 Optimal restoration of vision using any of these methods relies on the presence of intact ganglion cells, that are capable of passing information to higher brain centres.…”

Section: Inner Retinal Remodelling Following Photoreceptor Death and mentioning

confidence: 99%

Advances in understanding the mechanisms of retinal degenerations

Fletcher

2020

Clinical and Experimental Optometry

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Photoreceptor death is an important contributor to irreversible vision loss worldwide. In this review, I outline our work examining the role that purines, such as adenosine triphosphate (ATP), have in normal retinal function and in retinal disease. Our work shows that the actions of ATP, mediated by P2X receptors, are expressed in various retinal layers including photoreceptor terminals, and when stimulated by excessive levels of ATP is associated with rapid death of neurons. Treatment with a compound that blocks the action of P2X and some P2Y receptors reduces photoreceptor death in a mouse model of retinal degeneration. Our observations not only provide a means for developing a potential treatment for reducing photoreceptor death, but also provides a novel way of studying the neural plasticity effects that develop in the inner retina following photoreceptor death. There are a range of inner retinal changes that could influence the effectiveness of retinal prostheses. Indeed, using an ATP‐induced degeneration model, we established that the amount of electrical stimulation required to elicit a response in the visual cortex was affected by the level of glial scarring. However, changes in P2X7 receptor expression by OFF ganglion cells during retinal degeneration can also be exploited by photoswitches to restore light sensitivity to degenerated retinae. Finally, our work has also considered how P2X7 expression by innate immune cells, and its role as a scavenger receptor, contributes to age‐related macular degeneration (AMD). Our results show that loss of P2X7 function is associated with thickening of Bruch's membrane as well as increased risk of advanced disease in people with AMD. Overall, our work over the last 20 years highlights the importance of purinergic signalling in normal retinal function and retinal disease and suggest that developing therapies that target P2X7 function could be of benefit for these diseases.

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An update on retinal prostheses

Cited by 130 publications

References 111 publications

Human Eye Optics within a Non-Euclidian Geometrical Approach and Some Implications in Vision Prosthetics Design

Human Eye Optics within a Non-Euclidian Geometrical Approach and Some Implications in Vision Prosthetics Design

Oculomotor Responses to Dynamic Stimuli in a 44-Channel Suprachoroidal Retinal Prosthesis

Advances in understanding the mechanisms of retinal degenerations

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