Retinal Anatomy and Electrode Array Position in Retinitis Pigmentosa Patients After Argus II Implantation: An International Study

Gregori, Ninel Z.; Callaway, Natalia F.; Hoeppner, Catherine; Yuan, Alex; Rachitskaya, Aleksandra; Feuer, William J.; Ameri, Hossein; Arévalo, J. Fernando; Augustin, Albert J.; Birch, David G.; Dagnelie, Gislin; Grisanti, Salvatore; Davis, Janet L.; Hahn, Paul; Handa, James T.; Ho, Allen C.; Huang, Suber; Humayun, Mark S.; Iezzi, Raymond; Jayasundera, Thiran; Kokame, Gregg T.; Lam, Byron L.; Lim, Jennifer I.; Mandava, Naresh; Montezuma, Sandra R.; Koo, Lisa C. Olmos de; Szurman, Peter; Vajzovic, Lejla; Wiedemann, Peter; Weiland, James D.; Yan, Jiong; Zacks, David N.

doi:10.1016/j.ajo.2018.06.012

Cited by 22 publications

(28 citation statements)

References 21 publications

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“…Good retina apposition to the device is extremely important for efficient signal transduction to the visual cortex. While poor apposition often is seen postimplantation,26 in our study the excellent apposition of overlying retina to the device underneath was confirmed postoperatively by OCT.…”

Section: Discussionsupporting

confidence: 71%

Acute Rabbit Eye Model for Testing Subretinal Prostheses

Xiao

Huffman

et al. 2019

Trans. Vis. Sci. Tech.

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Subretinal prostheses are a novel technology for restoring useful vision in patients with retinitis pigmentosa or age-related macular degeneration. We characterize the surgical implantation technique and functional time window of an acute rabbit eye model for testing of human subretinal prostheses. Methods: Retinal prostheses were implanted subretinally in 26 rabbits using a twostep technique. Fundus imaging, fluorescein fundus angiography, and optical coherence topography (OCT) were conducted postoperatively from days 1 to 21 to monitor prosthesis positioning and retinal anatomic changes. Results: Successful implantation and excellent retina apposition were achieved in 84.6% of the rabbits. OCTs showed the overlying retina at full thickness for the first 2 days after implantation. Histology confirmed intact inner layers of the overlying retina until day 3. Progressive atrophy of the overlying retina was revealed by repeated OCTs; approximately 40% of the retina thickness remained on postoperative days 5 and 6. Conclusions: The two-step implantation technique works well for the rabbit eye model with human prostheses. Rabbit retina may be used for acute electrophysiologic testing of a retinal prosthesis, but is unsuitable for chronic studies due to the merangiotic retina and its limited time window of validity. Translational Relevance: The improved efficacy in prosthesis surgery using this technique will circumvent the challenges in animal models that provide human-like features critical for the transition into human clinical trials.

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Section: Discussionsupporting

confidence: 71%

Acute Rabbit Eye Model for Testing Subretinal Prostheses

Xiao

Huffman

et al. 2019

Trans. Vis. Sci. Tech.

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“…Through use of this software, the camera alignment process is simplified and comfort is determined under more real-world stimulation conditions [ 1 ]. Depending on the patient experience, the device can be reprogrammed on a regular basis for a readjustment in response to changes to the array or the patient’s responses to the electrode stimulation [ 5 , 6 ]. The brightness of perception and the number of electrodes that give the patient a perception may decrease over time.…”

Section: Methodsmentioning

confidence: 99%

Effect of the electrode array-retina gap distance on visual function in patients with the Argus II retinal prosthesis

et al. 2020

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Background Post-implantation visual outcomes in patients with the Argus II Retinal Prosthesis is dependent on a multitude of factors including the positioning of the electrode array on the retina. The purpose of this study is to determine whether the average electrode array-retina gap distance correlates with objective visual function outcomes and sensitivity detection thresholds in patients implanted with the Argus II Retinal Prosthesis. Methods Five patients with implantation of the Argus II Retinal Prosthesis were enrolled in this single-institution retrospective study. Patient demographics were collected from medical records. Visual function data (Square Localization [SL] and Direction of Motion [DOM]) and Optical Coherence Tomography (Cirrus HD-OCT) images were extracted retrospectively from the Argus II Retinal Prosthesis Post-Approval study. Visual function tests were performed with the device OFF and ON at each study visit. Electrode array-retina gap distances were measured at each of the array’s 60 electrodes using the Cirrus HD-OCT software in both the nasotemporal and superoinferior planes. Data was obtained at baseline, and post-operative month 1, month 3, month 6, and year 1. Sensitivity detection thresholds were obtained at the initial programming visit and each reprogramming session. Results Three patients performed significantly better in SL visual function testing with the device ON. Patients that worsened in visual function testing with the device ON in both SL and DOM testing had a statistically significant decrease in performance. The electrode array-retina gap distance was found to effect performance in SL testing in a patient-dependent manner. No effect was found between the electrode-array gap distance and DOM testing or sensitivity detection threshold. Conclusion Our results demonstrate that the electrode array-retina gap distance may affect visual function outcomes in SL testing in certain patients with the Argus II Retinal Prosthesis, and the direction and magnitude of this effect is likely patient-dependent. Furthermore, complete apposition between the electrode array and retina may not always be necessary to achieve optimal visual outcomes.

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“…The electric field above a stimulating electrode rapidly spreads in a lateral direction with distance above the electrode resulting in a loss of spatial confinement. Epi-retinal devices are intended to stimulate RGCs, however large electrode-retina gaps after surgery have been reported (Gregori et al, 2018). Sub-retinal devices stimulate nearby inner retinal neurons and thereby take advantage of the natural signal processing by sending signals in the direction that a healthy retina would normally employ.…”

Section: Limited Spatial Resolutionmentioning

confidence: 99%

“…First, the electrodes used for stimulation were very small, with diameters around 10 µm, and in direct contact with the retina surface (epi-retinal stimulation). Clinically available devices use electrode sizes much larger; and there is usually some separation in space between the target neurons and the electrodes (Gregori et al, 2018). Secondly, these studies recorded and analyzed limited number of neurons within certain cell types.…”

Section: Selective Activationmentioning

confidence: 99%

Stimulation Strategies for Improving the Resolution of Retinal Prostheses

et al. 2020

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Electrical stimulation using implantable devices with arrays of stimulating electrodes is an emerging therapy for neurological diseases. The performance of these devices depends greatly on their ability to activate populations of neurons with high spatiotemporal resolution. To study electrical stimulation of populations of neurons, retina serves as a useful model because the neural network is arranged in a planar array that is easy to access. Moreover, retinal prostheses are under development to restore vision by replacing the function of damaged light sensitive photoreceptors, which makes retinal research directly relevant for curing blindness. Here we provide a progress review on stimulation strategies developed in recent years to improve the resolution of electrical stimulation in retinal prostheses. We focus on studies performed with explanted retinas, in which electrophysiological techniques are the most advanced. We summarize achievements in improving the spatial and temporal resolution of electrical stimulation of the retina and methods to selectively stimulate neurons with different visual functions. Future directions for retinal prostheses development are also discussed, which could provide insights for other types of neuromodulatory devices in which high-resolution electrical stimulation is required.

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Retinal Anatomy and Electrode Array Position in Retinitis Pigmentosa Patients After Argus II Implantation: An International Study

Abstract: Progressive macular thickening under the array was common and corresponded to decreased electrode-retina gap over time. By month 12, the array was completely apposed to the macula in approximately half of the eyes.

Cited by 22 publications

References 21 publications

Acute Rabbit Eye Model for Testing Subretinal Prostheses

Acute Rabbit Eye Model for Testing Subretinal Prostheses

Effect of the electrode array-retina gap distance on visual function in patients with the Argus II retinal prosthesis

Stimulation Strategies for Improving the Resolution of Retinal Prostheses

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