Explainable AI for Retinal Prostheses: Predicting Electrode Deactivation from Routine Clinical Measures

To provide appropriate levels of stimulation, retinal prostheses must be calibrated to an individual’s perceptual thresholds (‘system fitting’). Nonfunctional electrodes may then be deactivated to reduce power consumption and improve visual outcomes. However, thresholds vary drastically not just across electrodes but also over time, thus calling for a more flexible electrode deactivation strategy. Here we present an explainable artificial intelligence (XAI) model fit on a large longitudinal dataset that can 1) predict at which point in time the manufacturer chose to deactivate an electrode as a function of routine clinical measures (‘predictors’) and 2) reveal which of these predictors were most important. The model predicted electrode deactivation from clinical data with 60.8% accuracy. Performance increased to 75.3% with system fitting data, and to 84% when thresholds from follow-up examinations were available. The model further identified subject age and time since blindness onset as important predictors of electrode deactivation. An accurate XAI model of electrode deactivation that relies on routine clinical measures may benefit both the retinal implant and wider neuroprosthetics communities.

85% Improved Optical Power Delivery to Epiretinal Prostheses Using Rigid Body Compensation Algorithm

Vision impairment caused by degenerative retinal pathologies such as age-related macular degeneration can be treated using retinal implants. Such devices receive power and data using cables passing through a permanent surgical incision in the eye wall (sclera), which increases risk to patients and surgical costs. A recently developed retinal implant design eliminates the necessity of the implant cable through a photonic power converter (PPC) which receives optical power and data through the pupil using an ellipsoidal reflector and microelectromechanical mirror. We present a misalignment compensation algorithm model that accounts for rigid body motions of the reflector relative to the eye, and applies correction to the mirror coordinates in the presence of angular misalignment of the reflector. We demonstrate that up to 85\% of the nominal optical power can be delivered to the implant with axial reflector misalignments up to 30 degrees using the compensation algorithm.

Micro-Fabrication of Components for a High-Density Sub-Retinal Visual Prosthesis

We present a retrospective of unique micro-fabrication problems and solutions that were encountered through over 10 years of retinal prosthesis product development, first for the Boston Retinal Implant Project initiated at the Massachusetts Institute of Technology and at Harvard Medical School’s teaching hospital, the Massachusetts Eye and Ear—and later at the startup company Bionic Eye Technologies, by some of the same personnel. These efforts culminated in the fabrication and assembly of 256+ channel visual prosthesis devices having flexible multi-electrode arrays that were successfully implanted sub-retinally in mini-pig animal models as part of our pre-clinical testing program. We report on the processing of the flexible multi-layered, planar and penetrating high-density electrode arrays, surgical tools for sub-retinal implantation, and other parts such as coil supports that facilitated the implantation of the peri-ocular device components. We begin with an overview of the implantable portion of our visual prosthesis system design, and describe in detail the micro-fabrication methods for creating the parts of our system that were assembled outside of our hermetically-sealed electronics package. We also note the unique surgical challenges that sub-retinal implantation of our micro-fabricated components presented, and how some of those issues were addressed through design, materials selection, and fabrication approaches.

Artificial Organs and Related Bioinorganic Materials

Bioinorganic compounds or materials play the momentous role in all living organisms. Artificial organs are generally defined as any device, machine or complex biological structure which is partially or completely synthetic in nature and that could be implanted or integrated into human body to perform the tasks of a particular biological structure which has been damaged and should be replaced due to some medical reasons. Various artificial organs like bone, heart, kidney, liver, lung, pancreas, skin, urinary bladder, auditory brainstem implant, bionic contact lens, cochlear implant, direct acoustic cochlear implant, retinal implant and visual prosthetic parts have been developed. In this paper we are disusing about artificial biomaterial and organs.