Summary for Publication
Imagine a photograph captured with a low number of pixels, blurry and faded colors so that you can’t recognize the message that is contained in it. Next to it imagine the same picture recorded with a high pixel camera and appropriate colors. This is what each of the 360 million hearing impaired individuals worldwide have to deal with in regard of hearing. Most of them say “I can hear that somebody is talking to me but I can’t understand the words”. Many of them never ask for help and isolate themselves from society, ask for sick leave and lose their jobs. A good proportion of the ones that manage to get advice and obtain a hearing device do not wear it because it is not sufficiently compensating their hearing impairment and it is not comfortable to be used. Hearing impairment/loss (HL) is the most common sensory deficit in humans. Auditory prostheses are used to compensate this deficit. However, the currently available hearing aids based on mechanical energy and cochlear implants using electrical energy are not always sufficiently supplying the hearing impaired population. The main reasons are insufficient frequency specificity, feedback, and discomfort due to occlusion effect and/or recurrent auditory canal inflammations. Alternative stimulation strategies are therefore needed for the therapy of hearing deficits. Light is a form of energy that can be very well focused, can be applied without the need of direct contact and may be the alternative energy for the stimulation of the hearing organ. In our ERC Grant LaserHearingAids we demonstrated that the light stimulation at ear drum level, using the optoacoustic effect, is possible. Based on this finding we developed a light pulse amplitude modulation strategy that allows the activation of each frequency of the audible spectrum using monochrome laser pulses. Our results sustained our hypothesizes that optical energy can be applied and used in a more precise manner than the mechanical or electrical energy and gives the option of very fine tuning for optoacoustic hearing devices increasing the acuity of hearing impaired.
Using the results of our ERC Starting Grant we work on the preparatory steps before building the prototype of the first optoacoustic hearing device for humans as descibed in the ERC Proof of Concept Grant LightCodesWords.
The electrophysiological studies confirmed a very precise activation of the individual targeted frequencies of the auditory spectrum using our laser pulse amplitude modulation paradigm. We published this work in Stahn et al. 2019.
We worked therefore on analyzing the safe range of levels of optoacoustic stimulation within the outer and middle ear and determined the further need to improve the used parameters based on the histology results. We discussed these issues at conferences and published the results Sorg et al. 2019.
Based on the needed steps described in the Proof of Concept proposal LIGHTCODESWORDS in preparation for building the prototype of the optoacoustic auditory prostheses we prepared a solid team capable to design the prototype of the optoacoustic hearing device and:
1. we tested the market confirming the need for our laser-based hearing device. We looked into building up cooperation with industry partners from the laser and hearing device industries as well as research Institutions.
2. we completed the biocompatibility studies for green laser light in tissues and cell cultures and defined limits for the laser stimulation with our currently used parameters. However, based on these results we had to postpone the ethical approvals for clinical studies until the encountered issues are solved.
3. for feasibility purposes of our stimulation paradigm we assessed the use of commercially available systems and look into the design of a cost-effective device.
4. in parallel, we work on coding speech and more complex sounds like e.g. music using the optoacoustic vibrations and improve loudness modulation within the biocompatibility margins.
Stahn P, Lim HH, Hinsberger MP, Sorg K, Pillong L, Kannengießer M, Schreiter C, Foth HJ, Langenbucher A, Schick B, Wenzel GI. Frequency-specific activation of the peripheral auditory system using optoacoustic laser stimulation. Sci Rep. 2019 Mar 12;9(1):4171. doi: 10.1038/s41598-019-40860-8.
Sorg K, Stahn P, Pillong L, Hinsberger MP, Heimann L, Foth HJ, Schick B, Wenzel GI. First biocompatibility margins for optical stimulation at the eardrum via 532-nm laser pulses in a mouse model. J Biomed Opt. 2019 Aug;24(8):1-10. doi: 10.1117/1.JBO.24.8.085003.
