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PLoS One. 2014 May 22;9(5):e97182. doi: 10.1371/journal.pone.0097182. eCollection 2014.

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

Author information

1
Bionics Institute, East Melbourne, Victoria, Australia; Department of Pathology, University of Melbourne, Parkville, Victoria, Australia.
2
Department of Pathology, University of Melbourne, Parkville, Victoria, Australia; Department of Anatomical Pathology, St Vincent's Hospital Melbourne, Fitzroy, Victoria, Australia.
3
Centre for Eye Research Australia, University of Melbourne, East Melbourne, Victoria, Australia; Department of Ophthalmology, The University of Melbourne, East Melbourne, Victoria, Australia.
4
Bionics Institute, East Melbourne, Victoria, Australia; Medical Bionics Department, University of Melbourne, East Melbourne, Victoria, Australia.
5
Centre for Eye Research Australia, University of Melbourne, East Melbourne, Victoria, Australia.
6
Department of Anatomical Pathology, St Vincent's Hospital Melbourne, Fitzroy, Victoria, Australia.
7
Statistical Consulting Centre, The University of Melbourne, Parkville, Victoria, Australia.
8
Bionics Institute, East Melbourne, Victoria, Australia.
9
Bionics Institute, East Melbourne, Victoria, Australia; Department of Otolaryngology, The University of Melbourne, East Melbourne, Victoria, Australia; Medical Bionics Department, University of Melbourne, East Melbourne, Victoria, Australia.
10
Bionics Institute, East Melbourne, Victoria, Australia; The HEARing Cooperative Research Centre, The University of Melbourne, East Melbourne, Victoria, Australia; Department of Otolaryngology, The University of Melbourne, East Melbourne, Victoria, Australia.
11
Bionics Institute, East Melbourne, Victoria, Australia; Department of Otolaryngology, The University of Melbourne, East Melbourne, Victoria, Australia.
12
Bionics Institute, East Melbourne, Victoria, Australia; Biomedical Engineering Department, Vanderbilt University, Nashville, Tennessee, United States of America.
13
Bionics Institute, East Melbourne, Victoria, Australia; Department of Pathology, University of Melbourne, Parkville, Victoria, Australia; Medical Bionics Department, University of Melbourne, East Melbourne, Victoria, Australia.

Abstract

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. Retinal integrity/function and the mechanical stability of the implant were assessed monthly using electroretinography (ERG), optical coherence tomography (OCT) and fundus photography. Electrode impedances were measured weekly and electrically-evoked visual cortex potentials (eEVCPs) were measured monthly to verify that chronic stimuli were suprathreshold. At the end of the chronic stimulation period, thresholds were confirmed with multi-unit recordings from the visual cortex. Randomized, blinded histological assessments were performed by two pathologists to compare the stimulated and non-stimulated retina and adjacent tissue.

RESULTS:

All subjects tolerated the surgical and stimulation procedure with no evidence of discomfort or unexpected adverse outcomes. After an initial post-operative settling period, electrode arrays were mechanically stable. Mean electrode impedances were stable between 11-15 kΩ during the implantation period. Visually-evoked ERGs & OCT were normal, and mean eEVCP thresholds did not substantially differ over time. In 81 of 84 electrode-adjacent tissue samples examined, there were no discernible histopathological differences between stimulated and unstimulated tissue. In the remaining three tissue samples there were minor focal fibroblastic and acute inflammatory responses.

CONCLUSIONS:

Chronic suprathreshold electrical stimulation of the retina using a suprachoroidal electrode array evoked a minimal tissue response and no adverse clinical or histological findings. Moreover, thresholds and electrode impedance remained stable for stimulation durations of up to 15 weeks. This study has demonstrated the safety and efficacy of suprachoroidal stimulation with charge balanced stimulus currents.

PMID:
24853376
PMCID:
PMC4031073
DOI:
10.1371/journal.pone.0097182
[Indexed for MEDLINE]
Free PMC Article

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