Characteristics of prosthetic vision in rats with subretinal flat and pillar electrode arrays

Elton Ho, Xin Lei, Thomas Anthony Flores, Henri Lorach, Tiffany W Huang, Ludwig Galambos, Theodore Kamins, James S Harris, Keith Mathieson, Daniel Palanker

Research output: Contribution to journalArticle

Abstract

Objective. Retinal prostheses aim to restore sight by electrically stimulating the surviving retinal neurons. In clinical trials of the current retinal implants, prosthetic visual acuity does not exceed 20/550. However, to provide meaningful restoration of central vision in patients blinded by age-related macular degeneration (AMD), prosthetic acuity should be at least 20/200, necessitating a pixel pitch of about 50 µm or lower. With such small pixels, stimulation thresholds are high due to limited penetration of electric field into tissue. Here, we address this challenge with our latest photovoltaic arrays and evaluate their performance in-vivo. 
Approach. We fabricated photovoltaic arrays with 55 and 40 µm pixels (a) in flat geometry, and (b) with active electrodes on 10 µm tall pillars. The arrays were implanted subretinally into rats with degenerate retina. Stimulation thresholds and grating acuity were evaluated using measurements of the visually evoked potentials (VEP). 
Main Results. With 55 μm pixels, we measured grating acuity of 48±11 μm, which matches the linear pixel pitch of the hexagonal array. This geometrically corresponds to a visual acuity of 20/192 in a human eye, matching the threshold of legal blindness in the US (20/200). With pillar electrodes, the irradiance threshold was nearly halved, and duration threshold reduced by more than 3-fold, compared to flat pixels. With 40 μm pixels, VEP was too low for reliable measurements of the grating acuity, even with pillar electrodes. 
Significance. While being helpful for treating a complete loss of sight, current prosthetic technologies are insufficient for addressing the leading cause of untreatable visual impairment - AMD. Subretinal photovoltaic arrays may provide sufficient visual acuity for restoration of central vision in patients blinded by AMD.
LanguageEnglish
JournalJournal of Neural Engineering
Early online date25 Jul 2019
DOIs
Publication statusE-pub ahead of print - 25 Jul 2019

Fingerprint

Macular Degeneration
Visual Acuity
Electrodes
Evoked Potentials
Visual Prosthesis
Retinal Neurons
Vision Disorders
Blindness
Retina
Clinical Trials
Technology

Keywords

  • retinal prostheses
  • retinal neurons
  • visual acuity
  • rats
  • photovoltaic arrays

Cite this

Ho, Elton ; Lei, Xin ; Flores, Thomas Anthony ; Lorach, Henri ; Huang, Tiffany W ; Galambos, Ludwig ; Kamins, Theodore ; Harris, James S ; Mathieson, Keith ; Palanker, Daniel. / Characteristics of prosthetic vision in rats with subretinal flat and pillar electrode arrays. In: Journal of Neural Engineering. 2019.
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abstract = "Objective. Retinal prostheses aim to restore sight by electrically stimulating the surviving retinal neurons. In clinical trials of the current retinal implants, prosthetic visual acuity does not exceed 20/550. However, to provide meaningful restoration of central vision in patients blinded by age-related macular degeneration (AMD), prosthetic acuity should be at least 20/200, necessitating a pixel pitch of about 50 µm or lower. With such small pixels, stimulation thresholds are high due to limited penetration of electric field into tissue. Here, we address this challenge with our latest photovoltaic arrays and evaluate their performance in-vivo. Approach. We fabricated photovoltaic arrays with 55 and 40 µm pixels (a) in flat geometry, and (b) with active electrodes on 10 µm tall pillars. The arrays were implanted subretinally into rats with degenerate retina. Stimulation thresholds and grating acuity were evaluated using measurements of the visually evoked potentials (VEP). Main Results. With 55 μm pixels, we measured grating acuity of 48±11 μm, which matches the linear pixel pitch of the hexagonal array. This geometrically corresponds to a visual acuity of 20/192 in a human eye, matching the threshold of legal blindness in the US (20/200). With pillar electrodes, the irradiance threshold was nearly halved, and duration threshold reduced by more than 3-fold, compared to flat pixels. With 40 μm pixels, VEP was too low for reliable measurements of the grating acuity, even with pillar electrodes. Significance. While being helpful for treating a complete loss of sight, current prosthetic technologies are insufficient for addressing the leading cause of untreatable visual impairment - AMD. Subretinal photovoltaic arrays may provide sufficient visual acuity for restoration of central vision in patients blinded by AMD.",
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Characteristics of prosthetic vision in rats with subretinal flat and pillar electrode arrays. / Ho, Elton; Lei, Xin; Flores, Thomas Anthony; Lorach, Henri; Huang, Tiffany W; Galambos, Ludwig; Kamins, Theodore; Harris, James S; Mathieson, Keith; Palanker, Daniel.

In: Journal of Neural Engineering, 25.07.2019.

Research output: Contribution to journalArticle

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T1 - Characteristics of prosthetic vision in rats with subretinal flat and pillar electrode arrays

AU - Ho, Elton

AU - Lei, Xin

AU - Flores, Thomas Anthony

AU - Lorach, Henri

AU - Huang, Tiffany W

AU - Galambos, Ludwig

AU - Kamins, Theodore

AU - Harris, James S

AU - Mathieson, Keith

AU - Palanker, Daniel

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N2 - Objective. Retinal prostheses aim to restore sight by electrically stimulating the surviving retinal neurons. In clinical trials of the current retinal implants, prosthetic visual acuity does not exceed 20/550. However, to provide meaningful restoration of central vision in patients blinded by age-related macular degeneration (AMD), prosthetic acuity should be at least 20/200, necessitating a pixel pitch of about 50 µm or lower. With such small pixels, stimulation thresholds are high due to limited penetration of electric field into tissue. Here, we address this challenge with our latest photovoltaic arrays and evaluate their performance in-vivo. Approach. We fabricated photovoltaic arrays with 55 and 40 µm pixels (a) in flat geometry, and (b) with active electrodes on 10 µm tall pillars. The arrays were implanted subretinally into rats with degenerate retina. Stimulation thresholds and grating acuity were evaluated using measurements of the visually evoked potentials (VEP). Main Results. With 55 μm pixels, we measured grating acuity of 48±11 μm, which matches the linear pixel pitch of the hexagonal array. This geometrically corresponds to a visual acuity of 20/192 in a human eye, matching the threshold of legal blindness in the US (20/200). With pillar electrodes, the irradiance threshold was nearly halved, and duration threshold reduced by more than 3-fold, compared to flat pixels. With 40 μm pixels, VEP was too low for reliable measurements of the grating acuity, even with pillar electrodes. Significance. While being helpful for treating a complete loss of sight, current prosthetic technologies are insufficient for addressing the leading cause of untreatable visual impairment - AMD. Subretinal photovoltaic arrays may provide sufficient visual acuity for restoration of central vision in patients blinded by AMD.

AB - Objective. Retinal prostheses aim to restore sight by electrically stimulating the surviving retinal neurons. In clinical trials of the current retinal implants, prosthetic visual acuity does not exceed 20/550. However, to provide meaningful restoration of central vision in patients blinded by age-related macular degeneration (AMD), prosthetic acuity should be at least 20/200, necessitating a pixel pitch of about 50 µm or lower. With such small pixels, stimulation thresholds are high due to limited penetration of electric field into tissue. Here, we address this challenge with our latest photovoltaic arrays and evaluate their performance in-vivo. Approach. We fabricated photovoltaic arrays with 55 and 40 µm pixels (a) in flat geometry, and (b) with active electrodes on 10 µm tall pillars. The arrays were implanted subretinally into rats with degenerate retina. Stimulation thresholds and grating acuity were evaluated using measurements of the visually evoked potentials (VEP). Main Results. With 55 μm pixels, we measured grating acuity of 48±11 μm, which matches the linear pixel pitch of the hexagonal array. This geometrically corresponds to a visual acuity of 20/192 in a human eye, matching the threshold of legal blindness in the US (20/200). With pillar electrodes, the irradiance threshold was nearly halved, and duration threshold reduced by more than 3-fold, compared to flat pixels. With 40 μm pixels, VEP was too low for reliable measurements of the grating acuity, even with pillar electrodes. Significance. While being helpful for treating a complete loss of sight, current prosthetic technologies are insufficient for addressing the leading cause of untreatable visual impairment - AMD. Subretinal photovoltaic arrays may provide sufficient visual acuity for restoration of central vision in patients blinded by AMD.

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KW - retinal neurons

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KW - photovoltaic arrays

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SN - 1741-2552

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