Oculomotor Responses to Dynamic Stimuli in a 44-Channel Suprachoroidal Retinal Prosthesis.

Purpose: To investigate oculomotor behavior in response to dynamic stimuli in retinal implant recipients.

Methods: Three suprachoroidal retinal implant recipients performed a four-alternative forced-choice motion discrimination task over six sessions longitudinally. Stimuli were a single white bar ("moving bar") or a series of white bars ("moving grating") sweeping left, right, up, or down across a 42″ monitor.

In vivo feasibility of epiretinal stimulation using ultrananocrystalline diamond electrodes.

Objective: Due to their increased proximity to retinal ganglion cells (RGCs), epiretinal visual prostheses present the opportunity for eliciting phosphenes with low thresholds through direct RGC activation. This study characterised the in vivo performance of a novel prototype monolithic epiretinal prosthesis, containing Nitrogen incorporated ultrananocrystalline (N-UNCD) diamond electrodes.

Approach: A prototype implant containing up to twenty-five 120 × 120 µm N-UNCD electrodes was implanted into 16 anaesthetised cats and attached to the retina either using a single tack or via magnetic coupling with a suprachoroidally placed magnet.

Safety Studies for a 44-Channel Suprachoroidal Retinal Prosthesis: A Chronic Passive Study.

Purpose: Following successful clinical outcomes of the prototype suprachoroidal retinal prosthesis, Bionic Vision Australia has developed an upgraded 44-channel suprachoroidal retinal prosthesis to provide a wider field of view and more phosphenes. The aim was to evaluate the preclinical passive safety characteristics of the upgraded electrode array.

Methods: Ten normal-sighted felines were unilaterally implanted with an array containing platinum electrodes (44 stimulating and 2 returns) on a silicone carrier near the area centralis.

Preclinical evaluation of a miniaturized Deep Brain Stimulation electrode lead.

The effect of miniaturizing the electrode lead for Deep Brain Stimulation (DBS) therapy was investigated in this work. A direct comparison was made between a miniature lead (0.65 mm diameter) and a lead of standard size (1.

First-in-human trial of a novel suprachoroidal retinal prosthesis.

Unlabelled: Retinal visual prostheses ("bionic eyes") have the potential to restore vision to blind or profoundly vision-impaired patients. The medical bionic technology used to design, manufacture and implant such prostheses is still in its relative infancy, with various technologies and surgical approaches being evaluated. We hypothesised that a suprachoroidal implant location (between the sclera and choroid of the eye) would provide significant surgical and safety benefits for patients, allowing them to maintain preoperative residual vision as well as gaining prosthetic vision input from the device.

Spatiotemporal interactions in the visual cortex following paired electrical stimulation of the retina.

Purpose: Retinal prostheses use spatiotemporal patterns of electrical stimulation across multiple electrodes to provide visual percepts to blind patients. It is generally assumed that percepts produced by individual electrodes are independent of one another, which may not be the case. In this study, we aimed to quantify interactions between pairs of electrical stimuli delivered to the retina.

Virtual electrodes by current steering in retinal prostheses.

Purpose: Retinal prostheses are an approved treatment for vision restoration in retinal degenerative diseases; however, present implants have limited resolution and simply increasing the number of electrodes is limited by design issues. In cochlear implants, virtual electrodes can be created by simultaneous stimulation of adjacent physical electrodes (current steering). The present study assessed whether this type of current steering can be adapted for retinal implants.

Safety and efficacy of explanting or replacing suprachoroidal electrode arrays in a feline model.

Background: A key requirement for retinal prostheses is the ability for safe removal or replacement. We examined whether suprachoroidal electrode arrays can be removed or replaced after implantation.

Methods: Suprachoroidal electrode arrays were unilaterally implanted into 13 adult felines.

Cortical activation following chronic passive implantation of a wide-field suprachoroidal retinal prosthesis.

Objective: The research goal is to develop a wide-field retinal stimulating array for prosthetic vision. This study aimed at evaluating the efficacy of a suprachoroidal electrode array in evoking visual cortex activity after long term implantation.

Approach: A planar silicone based electrode array (8 mm × 19 mm) was implanted into the suprachoroidal space in cats (ntotal = 10).

Chronic electrical stimulation with a suprachoroidal retinal prosthesis: a preclinical safety and efficacy study.

Purpose: To assess the safety and efficacy of chronic electrical stimulation of the retina with a suprachoroidal visual prosthesis.

Methods: Seven normally-sighted feline subjects were implanted for 96-143 days with a suprachoroidal electrode array and six were chronically stimulated for 70-105 days at levels that activated the visual cortex. Charge balanced, biphasic, current pulses were delivered to platinum electrodes in a monopolar stimulation mode.

Development of a surgical procedure for implantation of a prototype suprachoroidal retinal prosthesis.

Background: Current surgical techniques for retinal prosthetic implantation require long and complicated surgery, which can increase the risk of complications and adverse outcomes.

Method: The suprachoroidal position is known to be an easier location to access surgically, and so this study aimed to develop a surgical procedure for implanting a prototype suprachoroidal retinal prosthesis. The array implantation procedure was developed in 14 enucleated eyes.

Techniques for processing eyes implanted with a retinal prosthesis for localized histopathological analysis.

With the recent development of retinal prostheses, it is important to develop reliable techniques for assessing the safety of these devices in preclinical studies. However, the standard fixation, preparation, and automated histology procedures are not ideal. Here we describe new procedures for evaluating the health of the retina directly adjacent to an implant.

Suprachoroidal electrical stimulation: effects of stimulus pulse parameters on visual cortical responses.

Objective: Neural responses to biphasic constant current pulses depend on stimulus pulse parameters such as polarity, duration, amplitude and interphase gap. The objective of this study was to systematically evaluate and optimize stimulus pulse parameters for a suprachoroidal retinal prosthesis.

Approach: Normally sighted cats were acutely implanted with platinum electrode arrays in the suprachoroidal space.

A wide-field suprachoroidal retinal prosthesis is stable and well tolerated following chronic implantation.

Purpose: The safety of chronic implantation of a retinal prosthesis in the suprachoroidal space has not been established. This study aimed to determine the safety of a wide-field suprachoroidal electrode array following chronic implantation using histopathologic techniques and electroretinography.

Methods: A platinum electrode array in a wide silicone substrate was implanted unilaterally in the suprachoroidal space in adult cats (n = 7).

Visual cortex responses to single- and simultaneous multiple-electrode stimulation of the retina: implications for retinal prostheses.

Purpose: The aim of this study was to compare simultaneous stimulation of multiple electrodes to single-electrode stimulation in a retinal prosthesis.

Methods: A platinum electrode array was implanted into the suprachoroidal space in six normally sighted anesthetized cats. Multiunit activity from the primary visual cortex in response to retinal stimulation was recorded.

Visual cortex responses to suprachoroidal electrical stimulation of the retina: effects of electrode return configuration.

A clinically effective retinal prosthesis must evoke localized phosphenes in a retinotopic manner in response to stimulation of each of the retinal electrodes, evoke brightness cues over a wide dynamic range and function within safe stimulus limits. The effects of varying return configuration for retinal stimulation are currently unknown. To investigate this, we implanted a flexible, 7 × 12 electrode array into the suprachoroidal space of normally-sighted, anesthetized cats.

Wireless power delivery for retinal prostheses.

Delivering power to an implanted device located deep inside the body is not trivial. This problem is made more challenging if the implanted device is in constant motion. This paper describes two methods of transferring power wirelessly by means of magnetic induction coupling.

Development of a surgical approach for a wide-view suprachoroidal retinal prosthesis: evaluation of implantation trauma.

Background: Our research goal is to develop a safe, reproducible surgical approach for implantation of a wide-field retinal stimulating array. The aim of this study was to evaluate the pathological response to acute implantation of a functional prototype electrode array in the suprachoroidal space.

Methods: The surgical techniques to implant a 72 platinum electrode array fabricated on 8 × 13 × 0.

An automated system for rapid evaluation of high-density electrode arrays in neural prostheses.

The success of high-density electrode arrays for use in neural prostheses depends on efficient impedance monitoring and fault detection. Conventional methods of impedance testing and fault detection are time consuming and not always suited for in vivo assessment of high-density electrode arrays. Additionally, the ability to evaluate impedances and faults such as open and short circuits, both in vitro and in vivo, are important to ensure safe and effective stimulation.

Biocompatibility of immobilized aligned carbon nanotubes.

In vivo host responses to an electrode-like array of aligned carbon nanotubes (ACNTs) embedded within a biopolymer sheet are reported. This biocompatibility study assesses the suitability of immobilized carbon nanotubes for bionic devices. Inflammatory responses and foreign-body histiocytic reactions are not substantially elevated when compared to negative controls following 12 weeks implantation.

Cot-side electroencephalography for outcome prediction in preterm infants: observational study.

Objective: To assess the use of two-channel electroencephalographical (EEG) recordings for predicting adverse neurodevelopmental outcome (death or Bayley II mental developmental index/psychomotor developmental index < 70) in extremely preterm infants and to determine the relationship between quantitative continuity measures and a specialist neurophysiologist assessment of the same EEG segment for predicting outcome.

Design: Observational study.

Setting: The study was conducted in a neonatal intensive care unit.

Evaluation of stimulus parameters and electrode geometry for an effective suprachoroidal retinal prosthesis.

Several approaches have been proposed for placement of retinal prostheses: epiretinal, subretinal and suprachoroidal. We aimed to systematically evaluate the effectiveness of varying a range of stimulus parameters and electrode geometry for a suprachoroidal electrode array, using cortical evoked responses to monopolar electrical stimulation in cats. Our results indicate that charge thresholds were not dependent on electrode size, pulse widths or position of the return electrode tested, but were dependent on the number of sites stimulated in parallel.

Growth hormone receptor immunoreactivity is increased in the subventricular zone of juvenile rat brain after focal ischemia: a potential role for growth hormone in injury-induced neurogenesis.

Background: During recovery from an ischemic brain injury, a cerebral growth hormone (GH) axis is activated. Whilst GH has been demonstrated to be neuroprotective both in vitro and in vivo, a role for GH in neuro-restorative processes after brain injury has yet to be studied.

Objective: To explore a role for GH in injury-induced neurogenesis by examining GH receptor (GH-R) immunoreactivity within the subventricular zone (SVZ) of juvenile rats after brain injury and by testing the proliferative capacity of GH on embryonic mouse neural stem cells.

Cot-side electro-encephalography and interstitial glucose monitoring during insulin-induced hypoglycaemia in newborn lambs.

Background: The optimal approach to detection and management of neonatal hypoglycaemia remains unclear.

Objectives: We sought to demonstrate whether electro-encephalography (EEG) changes could be detected on the amplitude-integrated EEG monitor during induced hypoglycaemia in newborn lambs, and also to determine the accuracy of continuously measured interstitial glucose in this situation.

Methods: Needle electrodes were placed in the P3-P4, O1-O2 montages.