ADVERSE EVENTS OF THE ARGUS II RETINAL PROSTHESIS: Incidence, Causes, and Best Practices for Managing and Preventing Conjunctival Erosion

Nanocone-Array-Based Platinum-Iridium Oxide Neural Microelectrodes: Structure, Electrochemistry, Durability and Biocompatibility Study

Neural interfaces provide a window for bio-signal modulation and recording with the assistance of neural microelectrodes. However, shrinking the size of electrodes results in high electrochemical impedance and low capacitance, thus limiting the stimulation/recording efficiency. In order to achieve critical stability and low power consumption, here, nanocone-shaped platinum (Pt) with an extensive surface area is proposed as an adhesive layer on a bare Pt substrate, followed by the deposition of a thin layer of iridium oxide (IrO_x) to fabricate high-performance nanocone-array-based Pt-IrO_x neural microelectrodes (200 μm in diameter). A uniform nanocone-shaped Pt with significant roughness is created via controlling the ratio of NH₄⁺ and Pt⁴⁺ ions in the electrolyte, which can be widely applicable for batch production on multichannel flexible microelectrode arrays (fMEAs) and various substrates with different dimensions. The Pt-IrO_x nanocomposite-coated microelectrode presents a significantly low impedance down to 0.72 ± 0.04 Ω cm² at 1 kHz (reduction of ~92.95%). The cathodic charge storage capacity (CSC_c) and charge injection capacity (CIC) reaches up to 52.44 ± 2.53 mC cm^-2 and 4.39 ± 0.36 mC cm^-2, respectively. Moreover, superior chronic stability and biocompatibility are also observed. The modified microelectrodes significantly enhance the adhesion of microglia, the major immune cells in the central nervous system. Therefore, such a coating strategy presents great potential for biomedical and other practical applications.

INTRAOPERATIVE OPTICAL COHERENCE TOMOGRAPHY AND ENDOSCOPY-GUIDED EXPLANTATION OF ARGUS II DEVICE

PURPOSE

To describe a surgical approach using intraoperative optical coherence tomography and endoscopy for successful Argus II retinal prosthesis system removal.

METHODS

Retrospective review of a patient undergoing Argus II explantation 8 months after initial implantation.

RESULTS

Successful explantation of the Argus II device was performed in this patient.

CONCLUSION

Explantation of the Argus II device can be a difficult surgery, and intraoperative optical coherence tomography and endoscopy can be used to help avoid potential complications.

Improved performance and safety from Argus II retinal prosthesis post-approval study in France

PURPOSE

To evaluate the post-approval long-term outcomes of the Argus II Retinal Prosthesis, with a specific focus on its functional visual benefit in patients' daily activities.

METHODS

Eighteen patients with bare light perception due to end-stage retinitis pigmentosa were included in a French prospective, multicentre, single-arm study and followed for 2 years. Visual benefit in patients' daily activities was monitored through the use of the Functional Low-vision Observer Rated Assessment (FLORA), and the final score at 2 years was the primary effectiveness outcome. Standardized visual assessments were also performed. Device- or procedure-related adverse events were recorded.

RESULTS

Seventeen subjects completed the study. Positive impacts of the Argus II system on functional vision and well-being were demonstrated for over 70% of subjects on the FLORA. Among the daily activities/tasks tested, finding doorways was one of the most statistically significantly improved tasks (p < 0.001), along with estimating the size of an obstacle (p < 0.001), visually locating a place setting on a dining table (p < 0.001) and visually locating people in a non-crowded setting (p < 0.001). Visual function was improved on most standardized tests. Only two device- or procedure-related serious adverse events were observed (one vitreous haemorrhage and one endophthalmitis, both resolved with treatment). No explantation was required.

CONCLUSION

This first report of a completed post-approval study of Argus II with a two-year follow-up demonstrates the safety and effectiveness of the Argus II System in a real-world cohort of patients and further highlights its real functional benefit in implanted patients' daily activities.

What do blind people "see" with retinal prostheses? Observations and qualitative reports of epiretinal implant users

INTRODUCTION

Retinal implants have now been approved and commercially available for certain clinical populations for over 5 years, with hundreds of individuals implanted, scores of them closely followed in research trials. Despite these numbers, however, few data are available that would help us answer basic questions regarding the nature and outcomes of artificial vision: what do recipients see when the device is turned on for the first time, and how does that change over time?

METHODS

Semi-structured interviews and observations were undertaken at two sites in France and the UK with 16 recipients who had received either the Argus II or IRIS II devices. Data were collected at various time points in the process that implant recipients went through in receiving and learning to use the device, including initial evaluation, implantation, initial activation and systems fitting, re-education and finally post-education. These data were supplemented with data from interviews conducted with vision rehabilitation specialists at the clinical sites and clinical researchers at the device manufacturers (Second Sight and Pixium Vision). Observational and interview data were transcribed, coded and analyzed using an approach guided by Interpretative Phenomenological Analysis (IPA).

RESULTS

Implant recipients described the perceptual experience produced by their epiretinal implants as fundamentally, qualitatively different than natural vision. All used terms that invoked electrical stimuli to describe the appearance of their percepts, yet the characteristics used to describe the percepts varied significantly between recipients. Artificial vision for these recipients was a highly specific, learned skill-set that combined particular bodily techniques, associative learning and deductive reasoning in order to build a "lexicon of flashes"-a distinct perceptual vocabulary that they then used to decompose, recompose and interpret their surroundings. The percept did not transform over time; rather, the recipient became better at interpreting the signals they received, using cognitive techniques. The process of using the device never ceased to be cognitively fatiguing, and did not come without risk or cost to the recipient. In exchange, recipients received hope and purpose through participation, as well as a new kind of sensory signal that may not have afforded practical or functional use in daily life but, for some, provided a kind of "contemplative perception" that recipients tailored to individualized activities.

CONCLUSION

Attending to the qualitative reports of implant recipients regarding the experience of artificial vision provides valuable information not captured by extant clinical outcome measures.

One-Year Anatomical and Functional Outcomes of the Argus II Implantation in Korean Patients with Late-Stage Retinitis Pigmentosa: A Prospective Case Series Study

PURPOSE

To report the anatomical and functional outcomes of Argus II retinal prosthesis implantation in Korean patients.

METHODS

We included 5 consecutive patients with end-stage retinitis pigmentosa (RP) who underwent Argus II retinal prosthesis implantation and were followed for at least 12 months. The transcorneal electrical evoked response was utilized for patient selection. We used intraoperative optical coherence tomography (OCT) for optimal placement of the array and provided specialized vision rehabilitation training. A morphological evaluation using SD-OCT and a functional evaluation using computer-based visual function tests, a letter-reading ability test, and the Functional Low-Vision Observer Rated Assessment (FLORA) were conducted.

RESULTS

Postoperatively, the array was completely apposed to the retinal surface in all eyes, except for one eye which had a preexisting macular concavity. Fibrosis-like tissues of ≥50-μm thickness developed at the interface in 2 eyes. All of the patients showed improvement in computer-based visual function tests and could read ETDRS letters at a distance of 50 cm. Three patients could read Korean words. FLORA was improved in all patients, mainly in tasks of visual mobility, daily activities, and social interactions.

CONCLUSIONS

Along with good anatomical outcomes and specialized rehabilitation practices, recipients of the Argus II implant showed profound improvements in functional vision and mobility.

Inherited eye diseases in Turkey: Current approaches and future directions

The aim of this review is to reveal Turkey's current status of medical practice in inherited eye diseases and the necessary steps to improve healthcare services and research activities in this area. Since consanguinity rate is high, disease burden is estimated to be high in Turkey. Universal health insurance system, easily accessible medical specialists, increasing genetic test, and counseling opportunities are the key advantages of Turkey's healthcare system. However, specialized clinics for inherited eye diseases, low-vision rehabilitation services, training of ophthalmologists about the recent developments in ocular genetics, and multidisciplinary translational research are the main headlines needed to be focused for better health services and successful research in Turkey.

Optoelectronic Devices for Vision Restoration

PURPOSE OF REVIEW

The goal is providing an update to the latest research surrounding optoelectronic devices, highlighting key studies and benefits and limitations of each device.

RECENT FINDINGS

The Argus II demonstrated long-term safety after five-year follow-up. Due to lack of tack fixation, subretinal implants appear to displace over time. PRIMA's completed primate trial showed initial safety and potential for improved vision, resulting in ongoing clinical trials Bionic Vision Australia developed a new 44-electrode suprachoroidal device currently in a clinical trial. Orion (cortical stimulation) is currently undergoing a clinical trial to demonstrate safety.

SUMMARY

Devices using external camera for images are unaffected by corneal or lens opacities but disconnect eye movements from image perception, while the opposite is true for implants directly detecting light. Visual acuity provided by devices is more complicated than implant electrode density and new devices aim to target this with innovative approaches.

An update on retinal prostheses

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.

Micro/Nano Technologies for High-Density Retinal Implant

During the past decades, there have been leaps in the development of micro/nano retinal implant technologies, which is one of the emerging applications in neural interfaces to restore vision. However, higher feedthroughs within a limited space are needed for more complex electronic systems and precise neural modulations. Active implantable medical electronics are required to have good electrical and mechanical properties, such as being small, light, and biocompatible, and with low power consumption and minimal immunological reactions during long-term implantation. For this purpose, high-density implantable packaging and flexible microelectrode arrays (fMEAs) as well as high-performance coating materials for retinal stimulation are crucial to achieve high resolution. In this review, we mainly focus on the considerations of the high-feedthrough encapsulation of implantable biomedical components to prolong working life, and fMEAs for different implant sites to deliver electrical stimulation to targeted retinal neuron cells. In addition, the functional electrode materials to achieve superior stimulation efficiency are also reviewed. The existing challenge and future research directions of micro/nano technologies for retinal implant are briefly discussed at the end of the review.