Retinal stimulation strategies to restore vision: Fundamentals and systems

Retinal prostheses have been developed to fight blindness in people affected by outer retinal layer dystrophies. To date, few hundred patients have received a retinal implant. Inspired by intraocular lenses, we have designed a foldable and photovoltaic wide-field epiretinal prosthesis (named POLYRETINA) capable of stimulating wireless retinal ganglion cells. Here we show that within a visual angle of 46.3 degrees, POLYRETINA embeds 2215 stimulating pixels, of which 967 are in the central area of 5 mm, it is foldable to allow implantation through a small scleral incision, and it has a hemispherical shape to match the curvature of the eye. We demonstrate that it is not cytotoxic and respects optical and thermal safety standards; accelerated ageing shows a lifetime of at least 2 years. POLYRETINA represents significant progress towards the improvement of both visual acuity and visual field with the same device, a current challenging issue in the field.

/pdf/design-and-validation-of-a-foldable-and-photovoltaic-wide-35eg6e10b4.pdf

Design and validation of a foldable and photovoltaic wide-field epiretinal prosthesis

Purpose. To investigate the effects of age-related macular degeneration (ARMD) on mobility performance and to identify the vision determinants of mobility in subjects with ARMD.

Methods. Walking speed and the number of obstacle contacts made on a 79-m indoor mobility course were measured in 21 subjects with ARMD and 11 age-matched subjects with normal vision. The mobility measures were transformed to percentage preferred walking speed and contacts score. The vision functions assessed included binocular visual acuity, contrast sensitivity, and visual field.

Results. In this study, subjects with ARMD did not walk significantly slower or make significantly more obstacle contacts on the mobility course than the normally sighted subjects of similar age. Between 29% and 35% of the variance in the ARMD mobility performance was accounted for by visual field and contrast sensitivity measures. The most significant predictor of mobility performance scored as percentage preferred walking speed was the size of a binocular central scotoma.

Conclusion. As the size of a binocular central scotoma increases, mobility performance decreases.

Vision and mobility performance of subjects with age-related macular degeneration

Recent Advances in Neural Electrode-Tissue Interfaces.

In the last decade, various clinical trials proved the capability of visual prostheses, in particular retinal implants, to restore a useful form of vision. These encouraging results promoted the emerging of several strategies for neuronal stimulation aiming at the restoration of sight. Besides the traditional approach based on electrical stimulation through metal electrodes in the different areas of the visual path (e.g., the visual cortex, the lateral geniculate nucleus, the optic nerve, and the retina), novel concepts for neuronal stimulation have been mostly exploited as building blocks of the next generation of retinal implants. This review is focused on critically discussing recent major advancements in the field of retinal stimulation with particular attention to the findings in the application of novel concepts and materials. Last, the major challenges in the field and their clinical implications will be outlined.

/pdf/retinal-prostheses-progress-toward-the-next-generation-m6us9a2sp2.pdf

Retinal prostheses: progress toward the next generation implants

A packaged electronic device includes a flexible circuit structure and a die. The flexible circuit structure includes a first structural layer and electrical conductors. The die is bonded to the flexible circuit structure by a flexible attachment layer. The die includes interconnects in electrical contact with die circuitry and extending through the die, through the flexible attachment layer, and into electrical contact with respective electrical conductors at first ends. A flexible second structural layer is disposed on the die and exposed portions of the electrical conductors, wherein the die and the electrical conductors are encapsulated by the first structural layer and the second structural layer. The first structural layer and/or the second structural layer include a plurality of openings defining respective exposed areas on the electrical conductors at second ends.

Flexible electronic devices and related methods

The purpose of this paper is to present a wide field electrode array that may increase the field of vision in patients implanted with a retinal prosthesis. Mobility is often impaired in patients with low vision, particularly in those with peripheral visual loss. Studies on low vision patients as well as simulation studies on normally sighted individuals have indicated a strong correlation between the visual field and mobility. In addition, it has been shown that an increased visual field is associated with a significant improvement in visual acuity and object discrimination. Current electrode arrays implanted in animals or human vary in size; however, the retinal area covered by the electrodes has a maximum projected visual field of about 10 degrees. We have designed wide field electrode arrays that could potentially provide a visual field of 34 degrees, which may significantly improve the mobility. Tests performed on a mechanical eye model showed that it was possible to fix 10 mm wide flexible polyimide dummy electrode arrays onto the retina using a single retinal tack. They also showed that the arrays could conform to the inner curvature of the eye. Surgeries on an enucleated porcine eye model demonstrated feasibility of implantation of 10 mm wide arrays through a 5 mm eye wall incision.

/pdf/toward-a-wide-field-retinal-prosthesis-1w837pdyzo.pdf

Toward a wide-field retinal prosthesis.

Simulations of artificial vision suggest that 1000 electrodes may be required to restore vision to individuals with diseases of the outer retina. In order to achieve such an implant, new technology is needed, since the state-of-the-art implantable neural stimulator has at most 22 contacts with neural tissue. A critical component of this system is the multi-channel, stimulating electrode array. This array must meet very challenging, competing requirements for manufacturing, integration, surgical handling, and biocompatibility. Our lab has evaluated 3 polymers as retinal prosthesis substrates: polyimide, parylene, and silicone.

A comparison of retinal prosthesis electrode array substrate materials

A packaged electronic device includes a die, a flexible circuit structure, and a barrier film disposed on the die. The die includes die circuitry and electrical contacts. The flexible circuit structure is bonded directly to the die, and includes electrical conductors encapsulated by structural layers. Each electrical conductor contacts a respective electrical contact. The electronic device is encapsulated by the barrier film and one or more of the structural layers.

Electronic devices including flexible electrical circuits and related methods

Fabrication of electronic devices including flexible electrical circuits

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