gms | German Medical Science

Objective: Retinal prostheses aim to restore vision in patients with photoreceptor degeneration through electrical stimulation of the retina eliciting perception of a range of phosphenes. How effectively phosphenes can be combined to form complex images depends on their individual characteristics and their interactions. The goal of this study was to explore how meaningful patterns and images can be perceived through multiple electrode stimulation with a suprachoroidal retinal prosthesis.

Methods: Two patients with retinitis pigmentosa were implanted with a suprachoroidal electrode array. Several experiments were performed to investigate the perception of multiple electrode stimulation. In the first experiment, electrodes were stimulated to elicit the perception of simple recognisable patterns such as numbers or letters, which were then tested in a randomised forced choice recognition task. In a second experiment, multiple electrodes corresponding to images of white wedges oriented in four directions on a uniform background were stimulated. Patients were asked to identify wedge orientation. In a third experiment, the effect of eye tracking on orientation recognition was explored.

Results: Perception of simple patterns was possible in both patients. Accuracy of correctly identifying patterns at random ranged from 0-100%, depending on the patient and the pattern. In the second experiment, at 0% background intensity, P1 correctly identified pattern orientation with 100% accuracy, while P2 only scored up to 65% on average. Using background intensities up to 50%, P1 scored with at least 80% accuracy, which further reduced to a score of 20% at 90% background intensity. In the third experiment, eye tracking with P2 and movement of the visual field of interest based on the eye position was found to significantly increase his recognition scores up to 87.5% on average.

Discussion: The ability to identify patterns or pattern features demonstrates the capacity of the suprachoroidal device to provide meaningful information to visually impaired patients. In addition, compensating for eye movements is expected to significantly improve performance outcomes.

Acknowledgements: This work was supported by the Australian Research Council through its Special Research Initiative in Bionic Vision Science and Technology awarded to Bionic Vision Australia and by the Bertalli Family Foundation to the Bionics Institute. The Bionics Institute acknowledges the support received from the Victorian Government through its Operational Infrastructure Program. The Bionic Vision Australia Consortium consists of five member organizations (Centre for Eye Research Australia, Bionics Institute, NICTA, University of Melbourne and University of New South Wales) and three partner organizations (The Royal Victorian Eye and Ear Hospital, National Vision Research Institute of Australia and the University of Western Sydney). For this publication, the consortium members consist of (in alphabetical order): Penelope J Allen, Lauren N Ayton, Nick Barnes, Tamara-Leigh E Brawn, Robert Briggs, Anthony N Burkitt, Owen Burns, Robyn H Guymer, Nigel H Lovell, Chi D Luu, Chris D McCarthy, Mark McCombe, Hugh J McDermott, Michelle McPhedran, David AX Nayagam, Thushara Perera, Alexia Saunders, Adele F Scott, Kyle Slater, Ashley Stacey, Robert K Shepherd, Gregg J Suaning, Joel Villalobos, Chris E Williams and Jonathan Yeoh.