The Experts below are selected from a list of 1671 Experts worldwide ranked by ideXlab platform

Toshihiko Matsuo - One of the best experts on this subject based on the ideXlab platform.

  • modelling the visual response to an ourep Retinal Prosthesis with photoelectric dye coupled to polyethylene film
    Journal of Neural Engineering, 2021
    Co-Authors: Koichiro Yamashita, Toshihiko Matsuo, Tetsuya Uchida, Prathima Sundaram, Willy Wong
    Abstract:

    Objective.Retinal prostheses have been developed to restore vision in blind patients suffering from diseases like retinitis pigmentosa.Approach.A new type of Retinal Prosthesis called the Okayama University-type Retinal Prosthesis (OUReP) was developed by chemically coupling photoelectric dyes to a polyethylene film surface. The Prosthesis works by passively generating an electric potential when stimulated by light. However, the neurophysiological mechanism of how OUReP stimulates the degenerated retina is unknown.Main results.Here, we explore how the OUReP affects Retinal tissues using a finite element model to solve for the potential inside the tissue and an active Hodgkin-Huxley model based on rat vision to predict the corresponding Retinal bipolar response.Significance.We show that the OUReP is likely capable of eliciting responses in Retinal bipolar cells necessary to generate vision under most ambient conditions.

  • visual evoked potential recovery by subRetinal implantation of photoelectric dye coupled thin film Retinal Prosthesis in monkey eyes with macular degeneration
    Artificial Organs, 2018
    Co-Authors: Toshihiko Matsuo, Tetsuya Uchida, Koichiro Yamashita, Jun Sakurai, Chie Matsuo, Tomoaki Araki, Yusuke Yamashita, Kunihisa Kamikawa
    Abstract:

    Retinal Prosthesis or artificial retina is a promising modality of treatment for outer Retinal degeneration, caused by primary and secondary loss of photoreceptor cells, in hereditary Retinal dystrophy and age-related macular degeneration, respectively. Okayama University-type Retinal Prosthesis (OUReP) is a photoelectric dye-coupled polyethylene film which generates electric potential in response to light and stimulates nearby neurons. The dye-coupled films were implanted by vitreous surgery in the subRetinal space of monkey eyes with macular degeneration which had been induced by cobalt chloride injection from the scleral side. A pilot 1-month observation study involved 6 monkeys and a pivotal 6-month observation study involved 8 monkeys. Of 8 monkeys in 6-month group, 3 monkeys underwent dye-coupled film removal at 5 months and were observed further for 1 month. The amplitude of visual evoked potential which had been reduced by macular degeneration did recover at 1 month after film implantation and maintained the level at 6 months. Optical coherence tomography showed no Retinal detachment, and full-field electroretinograms maintained a-wave and b-wave amplitudes, indicative of no Retinal toxicity. Pathological examinations after 6-month implantation showed structural integrity of the inner Retinal layer in close apposition to dye-coupled films. The implanted films which were removed by vitrectomy 5 months later showed light-evoked surface electric potentials by scanning Kelvin probe measurement. The photoelectric dye-coupled film (OUReP), which serves as a light-receiver and a displacement current generator in the subRetinal space of the eye, has a potential for recovering vision in diseases with photoreceptor cell loss, such as retinitis pigmentosa and age-related macular degeneration.

  • visual evoked potential in rabbits eyes with subRetinal implantation by vitrectomy of okayama university type Retinal Prosthesis oureptm
    Journal of Veterinary Medical Science, 2018
    Co-Authors: Toshihiko Matsuo, Tetsuya Uchida, Koichiro Yamashita, Shigiko Takei, Daisuke Ido, Mamoru Tanaka, Masao Oguchi, Toshinori Furukawa
    Abstract:

    Okayama University-type Retinal Prosthesis (OURePTM) is a photoelectric dye-coupled polyethylene film which generates electric potential in response to light and stimulates nearby neurons. This study aims to test surgical feasibility for subRetinal film implantation and to examine functional durability of films in subRetinal space. Dye-coupled films were implanted subRetinally by vitrectomy in the right eye of normal white rabbits: 8 rabbits for 1 month and 8 rabbits for 6 months. The implanted films were removed by vitrectomy in 4 of these 8 rabbits in 1-month or 6-month implantation group. The films were also implanted in 4 rhodopsin-transgenic Retinal dystrophic rabbits. Visual evoked potential was measured before film implantation as well as 1 or 6 months after film implantation, or 1 month after film removal. The films were successfully implanted in subRetinal space of Retinal detachment induced by subRetinal fluid injection with a 38G polyimide tip. The retina was reattached by fluid-air exchange in vitreous cavity, Retinal laser coagulation, and silicone oil injection. The ratios of P2 amplitudes of visual evoked potential in the implanted right eye over control left eye did not show significant changes between pre-implantation and post-implantation or post-removal (paired t-test). In Kelvin probe measurements, 4 pieces each of removed films which were implanted for 1 or 6 months showed proportional increase of surface electric potential in response to increasing light intensity. The film implantation was safe and implanted films were capable of responding to light.

  • photoelectric dye used for okayama university type Retinal Prosthesis reduces the apoptosis of photoreceptor cells
    Journal of Ocular Pharmacology and Therapeutics, 2017
    Co-Authors: Shihui Liu, Toshihiko Matsuo, Osamu Hosoya, Tetsuya Uchida
    Abstract:

    Abstract Purpose: Our previous study demonstrated that photoelectric dye-coupled polyethylene film (Okayama University-type Retinal Prosthesis), which was implanted in subRetinal space of the eyes of Royal College of Surgeons (RCS) rats, prevented Retinal neurons from apoptotic death. In this study, we aimed to examine whether photoelectric dye itself would protect Retinal neurons from apoptosis in RCS rats. Methods: RCS rats received intravitreous injection of different concentrations of the dye in the left eye and housed under a 12-h light–dark cycle. Saline injection in the right eye served as control. In addition, RCS rats with dye injection were kept in 24-h daily dark condition. Sections were processed for terminal deoxynucleotidyl transferase-mediated fluorescein-conjugated-dUTP nick-end-labeling (TUNEL) assay and immunohistochemical staining of glial fibrillary acidic protein (GFAP) and protein kinase Cα (PKCα). Results: The number of TUNEL-positive cells significantly decreased in the retina of d...

  • visual evoked potential in rcs rats with okayama university type Retinal Prosthesis ourep implantation
    Journal of Artificial Organs, 2017
    Co-Authors: Toshihiko Matsuo, Osamu Hosoya, Tetsuya Uchida
    Abstract:

    Photoelectric dye-coupled polyethylene film, designated Okayama University type-Retinal Prosthesis or OUReP™, generates light-evoked surface electric potentials and stimulates neurons. The dye-coupled films or plain films were implanted subRetinally in both eyes of 10 Royal College of Surgeons rats with hereditary Retinal dystrophy at the age of 6 weeks. Visual evoked potentials in response to monocular flashing light stimuli were recorded from cranially-fixed electrodes, 4 weeks and 8 weeks after the implantation. After the recording, subRetinal film implantation was confirmed histologically in 7 eyes with dye-coupled films and 7 eyes with plain films. The recordings from these 7 eyes in each group were used for statistical analysis. The amplitudes of visual evoked potentials in the consecutive time points from 125 to 250 ms after flash were significantly larger in the 7 eyes with dye-coupled film implantation, compared to the 7 eyes with plain film implantation at 8 weeks after the implantation (P < 0.05, repeated-measure ANOVA). The photoelectric dye-coupled polyethylene film, as Retinal Prosthesis, gave rise to visual evoked potential in response to flashing light.

Lyndon Da Cruz - One of the best experts on this subject based on the ideXlab platform.

  • Advances in Retinal Prosthesis systems
    'SAGE Publications', 2019
    Co-Authors: Edward Bloch, Yvonne Luo, Lyndon Da Cruz
    Abstract:

    Retinal Prosthesis systems have undergone significant advances in the past quarter century, resulting in the development of several different novel surgical and engineering approaches. Encouraging results have demonstrated partial visual restoration, with improvement in both coarse objective function and performance of everyday tasks. To date, four systems have received marketing approval for use in Europe or the United States, with numerous others undergoing preclinical and clinical evaluation, reflecting the established safety profile of these devices for chronic implantation. This progress represents the first notion that the field of visual restorative medicine could offer blind patients a hope of real and measurable benefit. However, there are numerous complex engineering and biophysical obstacles still to be overcome, to reconcile the gap that remains between artificial and natural vision. Current developments in the form of enhanced image processing algorithms and data transfer approaches, combined with emerging nanofabrication and conductive polymerization techniques, herald an exciting and innovative future for Retinal prosthetics. This review provides an update of Retinal prosthetic systems currently undergoing development and clinical trials while also addressing future challenges in the field, such as the assessment of functional outcomes in ultra-low vision and strategies for tackling existing hardware and software constraints

  • five year safety and performance results from the argus ii Retinal Prosthesis system clinical trial
    Ophthalmology, 2016
    Co-Authors: Lyndon Da Cruz, Mark S. Humayun, Jessy D Dorn, Gislin Dagnelie, Paulo E Stanga, Josealain Sahel, James T Handa, Pierre Olivier Barale, Farhad Hafezi
    Abstract:

    Purpose The Argus II Retinal Prosthesis System (Second Sight Medical Products, Inc, Sylmar, CA) was developed to restore some vision to patients blind as a result of retinitis pigmentosa (RP) or outer Retinal degeneration. A clinical trial was initiated in 2006 to study the long-term safety and efficacy of the Argus II System in patients with bare or no light perception resulting from end-stage RP. Design Prospective, multicenter, single-arm clinical trial. Within-patient controls included the nonimplanted fellow eye and patients' native residual vision compared with their vision with the Argus II. Participants Thirty participants in 10 centers in the United States and Europe. Methods The worse-seeing eye of blind patients was implanted with the Argus II. Patients wore glasses mounted with a small camera and a video processor that converted images into stimulation patterns sent to the electrode array on the retina. Main Outcome Measures The primary outcome measures were safety (the number, seriousness, and relatedness of adverse events) and visual function, as measured by 3 computer-based, objective tests. Secondary measures included functional vision performance on objectively scored real-world tasks. Results Twenty-four of 30 patients remained implanted with functioning Argus II Systems at 5 years after implantation. Only 1 additional serious adverse event was experienced after the 3-year time point. Patients performed significantly better with the Argus II on than off on all visual function tests and functional vision tasks. Conclusions The 5-year results of the Argus II trial support the long-term safety profile and benefit of the Argus II System for patients blind as a result of RP. The Argus II is the first and only Retinal implant to have market approval in the European Economic Area, the United States, and Canada.

  • the argus ii Retinal Prosthesis system
    Progress in Retinal and Eye Research, 2016
    Co-Authors: Yvonne Hsulin Luo, Lyndon Da Cruz
    Abstract:

    The Argus(®) II Retinal Prosthesis System (Second Sight Medical Products) is the first prosthetic vision device to obtain regulatory approval in both Europe and the USA. As such it has entered the commercial market as a treatment for patients with profound vision loss from end-stage outer Retinal disease, predominantly retinitis pigmentosa. To date, over 100 devices have been implanted worldwide, representing the largest group of patients currently treated with visual prostheses. The system works by direct stimulation of the relatively preserved inner retina via epiRetinal microelectrodes, thereby replacing the function of the degenerated photoreceptors. Visual information from a glasses-mounted video camera is converted to a pixelated image by an external processor, before being transmitted to the microelectrode array at the macula. Elicited Retinal responses are then relayed via the normal optic nerve to the cortex for interpretation. We reviewed the animal and human studies that led to the development of the Argus(®) II device. A sufficiently robust safety profile was demonstrated in the phase I/II clinical trial of 30 patients. Improvement of function in terms of orientation and mobility, target localisation, shape and object recognition, and reading of letters and short unrehearsed words have also been shown. There remains a wide variability in the functional outcomes amongst the patients and the factors contributing to these performance differences are still unclear. Future developments in terms of both software and hardware aimed at improving visual function have been proposed. Further experience in clinical outcomes is being acquired due to increasing implantation.

  • the use of argus ii Retinal Prosthesis by blind subjects to achieve localisation and prehension of objects in 3 dimensional space
    Graefes Archive for Clinical and Experimental Ophthalmology, 2015
    Co-Authors: Lyndon Da Cruz, Yvonne Hsulin Luo, Joe Jianjiang Zhong
    Abstract:

    Background The Argus® II Retinal Prosthesis system has entered mainstream treatment for patients blind from Retinitis Pigmentosa (RP). We set out to evaluate the use of this system by blind subjects to achieve object localisation and prehension in 3-dimensional space.

  • visual and non visual navigation in blind patients with a Retinal Prosthesis
    PLOS ONE, 2015
    Co-Authors: Sara Garcia, Lyndon Da Cruz, Karin Petrini, Gary S Rubin, Marko Nardini
    Abstract:

    Human adults with normal vision can combine visual landmark and non-visual self-motion cues to improve their navigational precision. Here we asked whether blind individuals treated with a Retinal Prosthesis could also benefit from using the resultant new visual signal together with non-visual information when navigating. Four patients (blind for 15-52 years) implanted with the Argus II Retinal Prosthesis (Second Sight Medical Products Inc. Sylmar, CA), and five age-matched and six younger controls, participated. Participants completed a path reproduction and a triangle completion navigation task, using either an indirect visual landmark and non-visual self-motion cues or non-visual self-motion cues only. Control participants wore goggles that approximated the field of view and the resolution of the Argus II Prosthesis. In both tasks, control participants showed better precision when navigating with reduced vision, compared to without vision. Patients, however, did not show similar improvements when navigating with the Prosthesis in the path reproduction task, but two patients did show improvements in the triangle completion task. Additionally, all patients showed greater precision than controls in both tasks when navigating without vision. These results indicate that the Argus II Retinal Prosthesis may not provide sufficiently reliable visual information to improve the precision of patients on tasks, for which they have learnt to rely on non-visual senses.

Tetsuya Uchida - One of the best experts on this subject based on the ideXlab platform.

  • modelling the visual response to an ourep Retinal Prosthesis with photoelectric dye coupled to polyethylene film
    Journal of Neural Engineering, 2021
    Co-Authors: Koichiro Yamashita, Toshihiko Matsuo, Tetsuya Uchida, Prathima Sundaram, Willy Wong
    Abstract:

    Objective.Retinal prostheses have been developed to restore vision in blind patients suffering from diseases like retinitis pigmentosa.Approach.A new type of Retinal Prosthesis called the Okayama University-type Retinal Prosthesis (OUReP) was developed by chemically coupling photoelectric dyes to a polyethylene film surface. The Prosthesis works by passively generating an electric potential when stimulated by light. However, the neurophysiological mechanism of how OUReP stimulates the degenerated retina is unknown.Main results.Here, we explore how the OUReP affects Retinal tissues using a finite element model to solve for the potential inside the tissue and an active Hodgkin-Huxley model based on rat vision to predict the corresponding Retinal bipolar response.Significance.We show that the OUReP is likely capable of eliciting responses in Retinal bipolar cells necessary to generate vision under most ambient conditions.

  • visual evoked potential recovery by subRetinal implantation of photoelectric dye coupled thin film Retinal Prosthesis in monkey eyes with macular degeneration
    Artificial Organs, 2018
    Co-Authors: Toshihiko Matsuo, Tetsuya Uchida, Koichiro Yamashita, Jun Sakurai, Chie Matsuo, Tomoaki Araki, Yusuke Yamashita, Kunihisa Kamikawa
    Abstract:

    Retinal Prosthesis or artificial retina is a promising modality of treatment for outer Retinal degeneration, caused by primary and secondary loss of photoreceptor cells, in hereditary Retinal dystrophy and age-related macular degeneration, respectively. Okayama University-type Retinal Prosthesis (OUReP) is a photoelectric dye-coupled polyethylene film which generates electric potential in response to light and stimulates nearby neurons. The dye-coupled films were implanted by vitreous surgery in the subRetinal space of monkey eyes with macular degeneration which had been induced by cobalt chloride injection from the scleral side. A pilot 1-month observation study involved 6 monkeys and a pivotal 6-month observation study involved 8 monkeys. Of 8 monkeys in 6-month group, 3 monkeys underwent dye-coupled film removal at 5 months and were observed further for 1 month. The amplitude of visual evoked potential which had been reduced by macular degeneration did recover at 1 month after film implantation and maintained the level at 6 months. Optical coherence tomography showed no Retinal detachment, and full-field electroretinograms maintained a-wave and b-wave amplitudes, indicative of no Retinal toxicity. Pathological examinations after 6-month implantation showed structural integrity of the inner Retinal layer in close apposition to dye-coupled films. The implanted films which were removed by vitrectomy 5 months later showed light-evoked surface electric potentials by scanning Kelvin probe measurement. The photoelectric dye-coupled film (OUReP), which serves as a light-receiver and a displacement current generator in the subRetinal space of the eye, has a potential for recovering vision in diseases with photoreceptor cell loss, such as retinitis pigmentosa and age-related macular degeneration.

  • visual evoked potential in rabbits eyes with subRetinal implantation by vitrectomy of okayama university type Retinal Prosthesis oureptm
    Journal of Veterinary Medical Science, 2018
    Co-Authors: Toshihiko Matsuo, Tetsuya Uchida, Koichiro Yamashita, Shigiko Takei, Daisuke Ido, Mamoru Tanaka, Masao Oguchi, Toshinori Furukawa
    Abstract:

    Okayama University-type Retinal Prosthesis (OURePTM) is a photoelectric dye-coupled polyethylene film which generates electric potential in response to light and stimulates nearby neurons. This study aims to test surgical feasibility for subRetinal film implantation and to examine functional durability of films in subRetinal space. Dye-coupled films were implanted subRetinally by vitrectomy in the right eye of normal white rabbits: 8 rabbits for 1 month and 8 rabbits for 6 months. The implanted films were removed by vitrectomy in 4 of these 8 rabbits in 1-month or 6-month implantation group. The films were also implanted in 4 rhodopsin-transgenic Retinal dystrophic rabbits. Visual evoked potential was measured before film implantation as well as 1 or 6 months after film implantation, or 1 month after film removal. The films were successfully implanted in subRetinal space of Retinal detachment induced by subRetinal fluid injection with a 38G polyimide tip. The retina was reattached by fluid-air exchange in vitreous cavity, Retinal laser coagulation, and silicone oil injection. The ratios of P2 amplitudes of visual evoked potential in the implanted right eye over control left eye did not show significant changes between pre-implantation and post-implantation or post-removal (paired t-test). In Kelvin probe measurements, 4 pieces each of removed films which were implanted for 1 or 6 months showed proportional increase of surface electric potential in response to increasing light intensity. The film implantation was safe and implanted films were capable of responding to light.

  • photoelectric dye used for okayama university type Retinal Prosthesis reduces the apoptosis of photoreceptor cells
    Journal of Ocular Pharmacology and Therapeutics, 2017
    Co-Authors: Shihui Liu, Toshihiko Matsuo, Osamu Hosoya, Tetsuya Uchida
    Abstract:

    Abstract Purpose: Our previous study demonstrated that photoelectric dye-coupled polyethylene film (Okayama University-type Retinal Prosthesis), which was implanted in subRetinal space of the eyes of Royal College of Surgeons (RCS) rats, prevented Retinal neurons from apoptotic death. In this study, we aimed to examine whether photoelectric dye itself would protect Retinal neurons from apoptosis in RCS rats. Methods: RCS rats received intravitreous injection of different concentrations of the dye in the left eye and housed under a 12-h light–dark cycle. Saline injection in the right eye served as control. In addition, RCS rats with dye injection were kept in 24-h daily dark condition. Sections were processed for terminal deoxynucleotidyl transferase-mediated fluorescein-conjugated-dUTP nick-end-labeling (TUNEL) assay and immunohistochemical staining of glial fibrillary acidic protein (GFAP) and protein kinase Cα (PKCα). Results: The number of TUNEL-positive cells significantly decreased in the retina of d...

  • visual evoked potential in rcs rats with okayama university type Retinal Prosthesis ourep implantation
    Journal of Artificial Organs, 2017
    Co-Authors: Toshihiko Matsuo, Osamu Hosoya, Tetsuya Uchida
    Abstract:

    Photoelectric dye-coupled polyethylene film, designated Okayama University type-Retinal Prosthesis or OUReP™, generates light-evoked surface electric potentials and stimulates neurons. The dye-coupled films or plain films were implanted subRetinally in both eyes of 10 Royal College of Surgeons rats with hereditary Retinal dystrophy at the age of 6 weeks. Visual evoked potentials in response to monocular flashing light stimuli were recorded from cranially-fixed electrodes, 4 weeks and 8 weeks after the implantation. After the recording, subRetinal film implantation was confirmed histologically in 7 eyes with dye-coupled films and 7 eyes with plain films. The recordings from these 7 eyes in each group were used for statistical analysis. The amplitudes of visual evoked potentials in the consecutive time points from 125 to 250 ms after flash were significantly larger in the 7 eyes with dye-coupled film implantation, compared to the 7 eyes with plain film implantation at 8 weeks after the implantation (P < 0.05, repeated-measure ANOVA). The photoelectric dye-coupled polyethylene film, as Retinal Prosthesis, gave rise to visual evoked potential in response to flashing light.

Koichiro Yamashita - One of the best experts on this subject based on the ideXlab platform.

  • modelling the visual response to an ourep Retinal Prosthesis with photoelectric dye coupled to polyethylene film
    Journal of Neural Engineering, 2021
    Co-Authors: Koichiro Yamashita, Toshihiko Matsuo, Tetsuya Uchida, Prathima Sundaram, Willy Wong
    Abstract:

    Objective.Retinal prostheses have been developed to restore vision in blind patients suffering from diseases like retinitis pigmentosa.Approach.A new type of Retinal Prosthesis called the Okayama University-type Retinal Prosthesis (OUReP) was developed by chemically coupling photoelectric dyes to a polyethylene film surface. The Prosthesis works by passively generating an electric potential when stimulated by light. However, the neurophysiological mechanism of how OUReP stimulates the degenerated retina is unknown.Main results.Here, we explore how the OUReP affects Retinal tissues using a finite element model to solve for the potential inside the tissue and an active Hodgkin-Huxley model based on rat vision to predict the corresponding Retinal bipolar response.Significance.We show that the OUReP is likely capable of eliciting responses in Retinal bipolar cells necessary to generate vision under most ambient conditions.

  • visual evoked potential recovery by subRetinal implantation of photoelectric dye coupled thin film Retinal Prosthesis in monkey eyes with macular degeneration
    Artificial Organs, 2018
    Co-Authors: Toshihiko Matsuo, Tetsuya Uchida, Koichiro Yamashita, Jun Sakurai, Chie Matsuo, Tomoaki Araki, Yusuke Yamashita, Kunihisa Kamikawa
    Abstract:

    Retinal Prosthesis or artificial retina is a promising modality of treatment for outer Retinal degeneration, caused by primary and secondary loss of photoreceptor cells, in hereditary Retinal dystrophy and age-related macular degeneration, respectively. Okayama University-type Retinal Prosthesis (OUReP) is a photoelectric dye-coupled polyethylene film which generates electric potential in response to light and stimulates nearby neurons. The dye-coupled films were implanted by vitreous surgery in the subRetinal space of monkey eyes with macular degeneration which had been induced by cobalt chloride injection from the scleral side. A pilot 1-month observation study involved 6 monkeys and a pivotal 6-month observation study involved 8 monkeys. Of 8 monkeys in 6-month group, 3 monkeys underwent dye-coupled film removal at 5 months and were observed further for 1 month. The amplitude of visual evoked potential which had been reduced by macular degeneration did recover at 1 month after film implantation and maintained the level at 6 months. Optical coherence tomography showed no Retinal detachment, and full-field electroretinograms maintained a-wave and b-wave amplitudes, indicative of no Retinal toxicity. Pathological examinations after 6-month implantation showed structural integrity of the inner Retinal layer in close apposition to dye-coupled films. The implanted films which were removed by vitrectomy 5 months later showed light-evoked surface electric potentials by scanning Kelvin probe measurement. The photoelectric dye-coupled film (OUReP), which serves as a light-receiver and a displacement current generator in the subRetinal space of the eye, has a potential for recovering vision in diseases with photoreceptor cell loss, such as retinitis pigmentosa and age-related macular degeneration.

  • visual evoked potential in rabbits eyes with subRetinal implantation by vitrectomy of okayama university type Retinal Prosthesis oureptm
    Journal of Veterinary Medical Science, 2018
    Co-Authors: Toshihiko Matsuo, Tetsuya Uchida, Koichiro Yamashita, Shigiko Takei, Daisuke Ido, Mamoru Tanaka, Masao Oguchi, Toshinori Furukawa
    Abstract:

    Okayama University-type Retinal Prosthesis (OURePTM) is a photoelectric dye-coupled polyethylene film which generates electric potential in response to light and stimulates nearby neurons. This study aims to test surgical feasibility for subRetinal film implantation and to examine functional durability of films in subRetinal space. Dye-coupled films were implanted subRetinally by vitrectomy in the right eye of normal white rabbits: 8 rabbits for 1 month and 8 rabbits for 6 months. The implanted films were removed by vitrectomy in 4 of these 8 rabbits in 1-month or 6-month implantation group. The films were also implanted in 4 rhodopsin-transgenic Retinal dystrophic rabbits. Visual evoked potential was measured before film implantation as well as 1 or 6 months after film implantation, or 1 month after film removal. The films were successfully implanted in subRetinal space of Retinal detachment induced by subRetinal fluid injection with a 38G polyimide tip. The retina was reattached by fluid-air exchange in vitreous cavity, Retinal laser coagulation, and silicone oil injection. The ratios of P2 amplitudes of visual evoked potential in the implanted right eye over control left eye did not show significant changes between pre-implantation and post-implantation or post-removal (paired t-test). In Kelvin probe measurements, 4 pieces each of removed films which were implanted for 1 or 6 months showed proportional increase of surface electric potential in response to increasing light intensity. The film implantation was safe and implanted films were capable of responding to light.

Mark S. Humayun - One of the best experts on this subject based on the ideXlab platform.

  • Positive Visual Phenomena Following Implantation of the Argus II Retinal Prosthesis.
    Ophthalmic surgery lasers & imaging retina, 2017
    Co-Authors: Ama Sadaka, Cyrus Iqbal, Hossein Nazari, Shauna Berry, Charles C. Wykoff, Mark S. Humayun, Andrew G. Lee
    Abstract:

    A 62-year-old female who was legally blind secondary to retinitis pigmentosa (RP) developed new positive visual phenomena (PVP) ("visual storms") following implantation of the Argus II Retinal Prosthesis System (Second Sight Medical Products, Sylmar, CA). The potential mechanisms for the exacerbating PVP or hallucinatory release phenomena are proposed. Clinicians should be aware of these visual phenomena in patients with RP and the potential for worsening of or de novo development of PVP in patients considering the Argus II implant. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:1022-1025.].

  • five year safety and performance results from the argus ii Retinal Prosthesis system clinical trial
    Ophthalmology, 2016
    Co-Authors: Lyndon Da Cruz, Mark S. Humayun, Jessy D Dorn, Gislin Dagnelie, Paulo E Stanga, Josealain Sahel, James T Handa, Pierre Olivier Barale, Farhad Hafezi
    Abstract:

    Purpose The Argus II Retinal Prosthesis System (Second Sight Medical Products, Inc, Sylmar, CA) was developed to restore some vision to patients blind as a result of retinitis pigmentosa (RP) or outer Retinal degeneration. A clinical trial was initiated in 2006 to study the long-term safety and efficacy of the Argus II System in patients with bare or no light perception resulting from end-stage RP. Design Prospective, multicenter, single-arm clinical trial. Within-patient controls included the nonimplanted fellow eye and patients' native residual vision compared with their vision with the Argus II. Participants Thirty participants in 10 centers in the United States and Europe. Methods The worse-seeing eye of blind patients was implanted with the Argus II. Patients wore glasses mounted with a small camera and a video processor that converted images into stimulation patterns sent to the electrode array on the retina. Main Outcome Measures The primary outcome measures were safety (the number, seriousness, and relatedness of adverse events) and visual function, as measured by 3 computer-based, objective tests. Secondary measures included functional vision performance on objectively scored real-world tasks. Results Twenty-four of 30 patients remained implanted with functioning Argus II Systems at 5 years after implantation. Only 1 additional serious adverse event was experienced after the 3-year time point. Patients performed significantly better with the Argus II on than off on all visual function tests and functional vision tasks. Conclusions The 5-year results of the Argus II trial support the long-term safety profile and benefit of the Argus II System for patients blind as a result of RP. The Argus II is the first and only Retinal implant to have market approval in the European Economic Area, the United States, and Canada.

  • the bionic eye a quarter century of Retinal Prosthesis research and development
    Ophthalmology, 2016
    Co-Authors: Mark S. Humayun, Eugene De Juan, Gislin Dagnelie
    Abstract:

    This article describes the history of visual prostheses, with emphasis on the development of the Argus II Retinal Prosthesis system (Second Sight Medical Products, Inc., Sylmar, CA). A brief overview of cortical electrical stimulation in the blind is provided, followed by an account of the design and development of Retinal stimulation equipment at the Duke Eye Center in the late 1980s; the first human intraoperative tests there and the subsequent 8 years of tests at the Wilmer Eye Institute; the transfer of the project to the Doheny Eye Institute at the University of Southern California and the founding of Second Sight Medical Products; and the development and clinical trials of the Argus I and Argus II systems. In a series of vignettes, we pay tribute to the many colleagues and patient volunteers without whose help the work would not have been possible.

  • blind subjects implanted with the argus ii Retinal Prosthesis are able to improve performance in a spatial motor task
    British Journal of Ophthalmology, 2011
    Co-Authors: Ashish Ahuja, Mark S. Humayun, Jessy D Dorn, Avi Caspi, Matthew J Mcmahon, Gislin Dagnelie, Lyndon Dacruz, Paulo E Stanga, Robert J Greenberg
    Abstract:

    Background/aims To determine to what extent subjects implanted with the Argus II Retinal Prosthesis can improve performance compared with residual native vision in a spatial-motor task. Methods High-contrast square stimuli (5.85 cm sides) were displayed in random locations on a 19 99 (48.3 cm) touch screen monitor located 12 99 (30.5 cm) in front of the subject. Subjects were instructed to locate and touch the square centre with the system on and then off (40 trials each). The coordinates of the square centre and location touched were recorded. Results Ninety-six percent (26/27) of subjects showed a significant improvement in accuracy and 93% (25/27) show a significant improvement in repeatability with the system on compared with off (p<0.05, Student t test). A group of five subjects that had both accuracy and repeatability values <250 pixels (7.4 cm) with the system off (ie, using only their residual vision) was significantly more accurate and repeatable than the remainder of the cohort (p<0.01). Of this group, four subjects showed a significant improvement in both accuracy and repeatability with the system on. Conclusion In a study on the largest cohort of visual Prosthesis recipients to date, we found that artificial vision augments information from existing vision in a spatial-motor task. Clinical trials registry no NCT00407602.

  • a comparison of two and three dimensional dipole antennas for an implantable Retinal Prosthesis
    IEEE Transactions on Antennas and Propagation, 2008
    Co-Authors: S Soora, Mark S. Humayun, K Gosalia, Gianluca Lazzi
    Abstract:

    The feasibility is investigated using three dimensional folded dipole antennas as a data-telemetry implantable receiving antenna in a dual-unit Retinal Prosthesis to restore partial vision to the blind. Three dimensional designs are explored in an effort to enhance certain antenna characteristics such as bandwidth and maximum gain while reducing the planar footprint size in comparison to its two dimensional equivalent. The current vector alignment between the three dimensional layers are examined through folding and rotating the dipole arms with respect to each other to fully optimize the antenna's characteristics. The performance of the 2D and 3D antennas were compared in simulations and further examined by fabricating and characterizing the performance in a transmit/ receive system in air and inside eye phantoms. Results show that three-dimensional antennas can provide larger bandwidth while being physically smaller than the correspondent two-dimensional ones, thus providing larger channel capacity that could lead to a system with an increased number of stimulating electrodes.