The recent conclusion of our Generation Two suprachoroidal retinal prosthesis feasibility trial for people with late-stage inherited retinal disease (NCT03406416) was exciting because we could publish results demonstrating the devices’ stability, both in position and performance, as well as positive outcomes for participants both in the lab and at home.
This followed on from our 2012-2014 (NCT01603576) proof-of-concept prototype trial which showed electrical stimulation within the suprachoroidal space would result in reliable phosphenes (artificial visual impulses).
However, the device does not provide complete independence. We are keen to improve its performance to better support current and potential future users.
Patients were questioned about aspects of vision processing that would be more helpful to them. They spoke about the social isolation of profound visual loss and identified several features they felt would be helpful.
A particular request was the ability to detect a face, so people can be differentiated from objects at the same height. This would be useful when walking in the street, and when speaking to someone so they can direct their conversation towards a forward-facing person.
Additionally, the ability to identify an empty chair in a café or other social situations was also felt to be useful for social engagement. The ability to gauge proximity of objects was also identified as useful for navigation.
Following the Generation Two trial we immediately obtained ethics approval to enrol the same participants in further work, firstly to continue monitoring the devices within the eye and secondly to use new vision-processing algorithms to try and achieve these aims.
Ensuring the safety of a retinal prosthesis within the eye for the lifetime of the user is crucial. When we design the suprachoroidal retinal prosthesis we use materials and methods with this aim in mind.
We were fortunate to be able to use biocompatible platinum and silicone – materials that had been used in many prosthetic devices in the past – and conducted extensive testing of the intraocular components and lead wires prior to any participant implantation surgery.
However, regular ocular health checks conducted by clinical examination, fundus photography and OCT are also vital to demonstrate the long-term viability of the suprachoroidal approach. Hence, we are collecting a further five years of ocular health data.
New vision processing algorithms developed by our long-term collaborator Professor Nick Barnes from Australian National University and our commercial partner Bionic Vision Technologies have addressed some of the social isolation issues identified by our participants.
We have been testing these new algorithms in comparison with our original comprehensive vision processing algorithm developed by Professor Barnes. The results of this testing have been submitted for publication.
More than 35 groups from around the world have been working on visual prostheses. Most are intraocular, but a few groups are working on cortical prostheses which connect directly to the visual cortex at the back of the brain.
The three groups who have achieved European or US regulatory approval for retinal prostheses for use in patients with profound visual loss due to retinal dystrophies have unfortunately ceased production of their devices due to a combination of either technical failure, limited market penetration and/or poor patient outcomes.
Bionic Vision Technologies continues to work towards commercialisation of the suprachoroidal retinal prosthesis – improving functionality of the devices to provide better experiences for participants is vital to achieving this.
Our past work has demonstrated the ease of the surgical approach, the devices are stable within the eye, and their performance is reliable.
We continue to actively collect data on ocular health to confirm the feasibility of long-term implantation of our devices and ongoing performance. We also continue to seek input from our current participants to identify further improvements in vision processing, aiming to enhance their daily living.
ABOUT THE AUTHOR:
Name: A/Prof Penelope Allen
Qualifications: MBBS, FRANZCO
Affiliations: Centre for Eye Research Australia (CERA), Melbourne Retina Associates
Location: Melbourne
Years in industry: 30
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