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Retinal prostheses are designed to restore a basic sense of sight to people with profound vision loss. They require a relatively intact posterior visual pathway (optic nerve, lateral geniculate nucleus and visual cortex). Retinal implants are options for people with severe stages of retinal degenerative disease such as retinitis pigmentosa and age-related macular degeneration. There have now been three regulatory-approved retinal prostheses. Over five hundred patients have been implanted globally over the past 15 years. Devices generally provide an improved ability to localize high-contrast objects, navigate, and perform basic orientation tasks. Adverse events have included conjunctival erosion, retinal detachment, loss of light perception, and the need for revision surgery, but are rare. There are also specific device risks, including overstimulation (which could cause damage to the retina) or delamination of implanted components, but these are very unlikely. Current challenges include how to improve visual acuity, enlarge the field-of-view, and reduce a complex visual scene to its most salient components through image processing. This review encompasses the work of over 40 individual research groups who have built devices, developed stimulation strategies, or investigated the basic physiology underpinning retinal prostheses. Current technologies are summarized, along with future challenges that face the field., Competing Interests: Funding and Declaration of Competing Interest LA receives licensing royalties for purchase by commercial entities for the IVI-VLV tool and is supported by a NHMRC Next Generation Fellowship (1151055) and an NHMRC Project Grant (1082358). GD is a consultant to Second Sight Medical Products (USA), and receives licensing royalties for purchase by commercial entities for the ULV-VFQ tool. JW is a consultant to Second Sight Medical Products (USA). BJ is supported by NIH grants R01 EY015128, R01 EY028927, a P30 EY014800 Vision Core Grant and an unrestricted grant from Research to Prevent Blindness to the Moran Eye Center. RH is an employee of Pixium Vision (France). MM is a consultant to Pixium Vision (France) and receives support from the National Institute for Health Research (NIHR) London Biomedical Research Centre (BRC) at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology. MP and NB receive funding from Bionic Vision Technologies (Australia). DR is supported by the German Ministry for Education and Research, BMBF 031a308., (Copyright © 2019 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Purpose: The Argus I implant is the first-generation epiretinal prosthesis approved for an investigational clinical trial by the United States Food and Drug Administration. Herein we report testing results obtained from a 10-year follow-up to study the physiologic effects of the bioelectronic visual implant after prolonged chronic electrical stimulation., Design: Case report., Participant: One man, 55 years of age when enrolled in the study, underwent surgical implantation of the Argus I in June 2004, followed by periodic tests from July 2004 through June 2014, spanning a total of 10 years., Methods: The decade-long follow-up consisted of implant system performance tests, subject visual function evaluation, and implant-retina interface analysis., Main Outcome Measures: Changes in electrode impedance and perceptual threshold over the time course; subject's performance on visual function task, orientation, and mobility tests; and optical coherence tomography data, fundus imaging, and fluorescein angiography results for the assessment of subject's implant-retina physical interface., Results: Electrically elicited phosphenes were present 10 years after implantation of an epiretinal stimulator. The test subject not only was able to perceive phosphenes, but also could perform visual tasks at rates well above chance., Conclusions: This decade-long follow-up report provides further support for the use of retinal prostheses as a long-lasting treatment for some types of blindness., (Copyright © 2015 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

The aim of this study is to examine the relationship between vitreous temperature and posterior vitreous detachment (PVD). 30 porcine eyes were hemisected to form eyecups. In 10 eyes, the vitreous was warmed to 37 ± 1°C for 1 min and cooled down to room temperature. In 10 eyes, the vitreous was warmed to 44 ± 1°C for 1 min and cooled down to room temperature. 10 eyes were kept at room temperature. The vitreous was then removed surgically by forceps. In the eyes that were kept at room temperature (n=10), and in the eyes that the vitreous was warmed to 37 ± 1°C (n=10), the vitreous removal caused significant retinal damage, detachment and fold, and choroidal detachment. In the eyes that the vitreous was warmed to 44 ± 1°C (n=10), the vitreous removal did not cause any observable changes in the retina and choroid. Therefore, the vitreous separates from the retina after warming to 44 ± 1°C. The effect is likely irreversible through vitreous liquefaction. Thermal effect might have caused PVD in some patients. Since cell death occurs at above 55-58°C, the effect can potentially be safe and beneficial in surgical separation of the vitreous. Evidence is provided to show that this technique could be safely performed in vivo in humans, and that it would lead to safer removal of the vitreous during vitrectomy with fewer post-operative complications., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Objective: The objective was to evaluate magnetic resonance imaging (MRI) issues (magnetic field interactions, heating, artifacts and functional alterations) at 1.5 T and 3 T for the Argus II Retinal Prosthesis (Second Sight Medical Products, Sylmar, CA, USA)., Materials and Methods: Standardized protocols were used to assess magnetic field interactions (translational attraction and torque; 3 T, worst case), MRI-related heating (1.5 and 3 T), artifacts (3 T; worst case) and functional changes (1.5 and 3 T) associated with MRI., Results: The magnetic field interactions were acceptable. MRI-related heating, which was studied at a relatively high, MR system-reported whole body averaged specific absorption rates, will not pose a hazard to the patient under the conditions used for testing. While artifacts were "moderate" in relation to the dimensions of the Argus II Retinal Prosthesis, optimization of MRI parameters can reduce the size of the artifacts. Exposures to MRI conditions at 1.5 and 3 T did not damage or alter the functional aspects of the Argus II Retinal Prosthesis., Conclusions: In consideration of the test results, a patient with the Argus II Retinal Prosthesis may undergo MRI at 1.5 T or 3 T when specific guidelines and MRI conditions are followed, including those advised by the manufacturer., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Agar is a biological polymer, frequently used in tissue engineering research; due to its consistency, controllable size, and concentration-based properties, it often serves as a representative material for actual biological tissues. In this study, nanoindentation was used to characterize both the time-independent and time-dependent response of agar samples having various concentrations (0.5%-5.0% by weight). Quasi-static indentation was performed at different loads and depths using both open- and closed-loop controls. Reduced modulus (Er) values change with agar concentration, ranging from ∼30 kPa for 0.5% samples to ∼700 kPa for 5.0% samples, which is the same modulus range as usually encountered in soft biological materials. Dynamic indentation was performed to assess the effects of load, dynamic frequency and amplitude. Storage modulus values ranged from approximately 30 to 2300 kPa depending on agar concentration. Loss modulus remained consistently less than 30 kPa at all conditions, indicating a diminished damping response in agar., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Unlabelled: Degenerative diseases such as age-related macular degeneration (AMD) and retinitis pigmentosa (RP) primarily affect the photoreceptors, ultimately resulting in significant loss of vision. Retinal prostheses aim to elicit neural activity in the remaining retinal cells by detecting and converting light into electrical stimuli that can then be delivered to the retina. The concept of visual prostheses has existed for more than 50 years and recent progress shows promise, yet much remains to be understood about how the visual system will respond to artificial input after years of blindness that necessitate this type of prosthesis. This review focuses on 3 major areas: the histopathologic features of human retina affected by AMD and RP, current results from clinical trials, and challenges to overcome for continued improvement of retinal prostheses., Financial Disclosure(s): Proprietary or commercial disclosures may be found after the references., (Copyright © 2011 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)