Hearing impairment (HI) is the most prevalent sensory deficit worldwide and is associated with significant socio-economic burden. Disabling HI [i.e., a pure tone threshold of greater than 35 decibels (dB) in the better hearing ear] (WHO, 2021) affects people of all age groups. One to two out of 1,000 babies are born with disabling HI (Morton and Nance, 2006), and the probability of developing HI increases with age; approximately one-third of individuals with disabling HI are over the age of 65 (Livingston et al., 2017). Unmanaged HI limits an individual’s ability to communicate and interact with others. In children, unmanaged HI affects or even prevents acquisition of vocal speech (Kral et al., 2016). Reduced social interaction due to HI in adults can be a major burden to their private and professional lives. Furthermore, HI has a massive impact on quality of life, especially in elderly patients. In the elderly HI is associated with a greater risk of cognitive decline (Loughrey et al., 2018), depression and anxiety disorders (Cosh et al., 2018; Montero-Odasso et al., 2020; Huang et al., 2022).

Causal treatments options for disabling HI–such as gene replacement or supplementation therapy, are currently being explored; yet none have achieved approval for clinical application. For mild to moderate hearing loss, reduced cochlear sensitivity can be compensated by conventional hearing aids which primarily amplify sounds. However, hearing aids do not sufficiently help in more severe cases in which sensory inner hair cells are missing or dysfunctional. In the majority of such cases, the current treatment of choice is an electrical cochlear implant (eCI) which directly stimulates the spiral ganglion neurons (SGNs). Arguably the most successful neuroprothesis, the eCI partially restores hearing and enables speech perception in the majority of the more than one million users. Despite its success, users do not experience full hearing restoration and report significant limitations in their daily lives. Specifically, users typically have difficulty understanding speech in group conversations and/or noisy and reverberating background, with complex acoustic sounds such as music, and with perception use of tonality and voice inflection (Caldwell et al., 2017).

Currently, several innovations of hearing restoration are in preclinical development. One of them is the optical cochlear implant (oCI) (Moser, 2015; Dieter et al., 2020a; Kleinlogel et al., 2020). Making use of light through optogenetics, the oCI would optically stimulate SGNs within the cochlea. Specifically, non-disease-causing viral vectors shall be introduced into the cochlea, to render SGNs light-sensitive by transgenic expression of light-activated ion channels known as Channelrhodopsins (ChR) (Hernandez et al., 2014; Duarte et al., 2018; Keppeler, 2018; Wrobel et al., 2018). Following viral transduction of the SGNs, the genetic code of the ChR is transcribed under the control of a cell-specific promoter. When ChR-expressing SGNs are exposed to light a flux of ions rush into the cells, leading to their depolarization which then induces an action potential, thus, activating the auditory pathway (Dieter et al., 2020a). As light can be better confined in space than electrical current, the oCI can make better use of the tonotopic coding of sound frequency in the mammalian cochlea and thus transmit more spectral information about sound, promising a near natural hearing perception (Hernandez et al., 2014; Dieter et al., 2019, 2020b; Keppeler et al., 2020). Preclinical evidence suggests that single dosing of a viral vector carrying a ChR under control of the neural synapsin promoter enables a stable and overall safe ChR expression (Mager et al., 2018; Bali et al., 2022). Although there is considerable experimental evidence to support its clinical promise, only an evaluation of the oCI in human participants will determine if this technology can, indeed, improve hearing in people affected by disabling HI.

It is well-documented that the translation from preclinical experiments to clinical investigation is wrought with high rates of failure, significant costs, and large timelines; which presents a contentious issue in the scientific community (Begley and Ellis, 2012; Landis et al., 2012; Chalmers et al., 2014; Ioannidis et al., 2014). Although there are many complex steps in translation, and thus, potential areas that may contribute to translational challenges, it has been suggested that engagement of patients in the research process could lead to greater chances of success in clinical trials (Duffett, 2017). Partnering with patients in medical research can help to identify research gaps and priorities, which may improve the relevance of research findings and lead to more tangible impacts in patients’ daily lives. As experts of their lived health conditions, patients can provide valuable insight into the challenges and unmet needs of the current treatment options available to them (Foster et al., 2020). Thus, in preparation for a planned first-in-human clinical trial of the oCI, we sought to identify needs and preferences regarding a new cochlear implant (CI), as well as barriers to hypothetically receiving this novel CI.

The survey was distributed to 180 patients in the Ear Clinic of Göttingen’s Department of Otolaryngology from May to November 2020 (approximately 6 months), and 81 participants returned a completed questionnaire (response rate of 45%). Sixty-eight percent of participants were over the age of 60 years; and 58 (72%) were unilaterally fitted with a CI (59% with left ear implanted). Of participants that had an implant in one ear, 72% wore a hearing aid in the contralateral ear and eight (14%) could hear normally in the other ear. Participant demographics and characteristics of their CI can be found in Tables 1, 2.

In this study, we identified CI users’ perspectives and experiences with artificial hearing as well as their preferences and willingness to try a newly developed CI. We found that with current hearing rehabilitation technologies, patients’ needs are not fully being addressed. Taken together, this work provides valuable information for the design and planning of a future early-phase clinical trial for a new CI in development—such as the optical CI.

We found that in general, participants felt that all hypothetical improvements were important. This is not surprising, as these improvements address the unmet needs and significant limitations that CI users currently experience in their day-to-day lives (Dieter et al., 2020a; Kleinlogel et al., 2020). This finding is corroborated by the ample literature documenting that CI users experience more difficulties in acoustic environments common to daily situations than their normal-hearing peers. Although much work is continuously devoted to improving the eCI, such as improved sound processing and multipolar stimulation, these advancements cannot fully address the prevailing limitations of inadequate spectral, fine-temporal, and dynamic range representation that are inherent of electrical artificial hearing (Zhou et al., 2020). This suggests that a novel modality of stimulation for artificial hearing, such as optical stimulation, would be warranted. In vivo and in silico preclinical studies confirmed the expectation that the oCI achieves near physiological (i.e., acoustic/natural hearing) spectral selectivity (Dieter et al., 2019, 2020b; Keppeler et al., 2020; Khurana et al., 2022), fundamentally exceeding that of state-of-the-art eCI, thereby promising more independent stimulation channels in the oCI than amenable to the eCI (≤10). Moreover, preclinical studies suggest an increased output dynamic range using the oCI over the eCI (Bali et al., 2021). Providing CI users with more spectral and intensity information is expected to improve the understanding of speech in multi-speaker situations as well as with fluctuating background noise, which remains a challenge with the eCI (Zheng et al., 2021). Considering these fundamental improvements to artificial hearing, it is conceivable that CI users who are unsatisfied with their current eCI would benefit from and would be open to an oCI (e.g., in the other ear not yet implanted), granted that it would indeed address the current limitations of the eCI.

Interestingly, regarding the hypothetical risks and drawbacks associated with a new CI, participants appeared to have fewer concerns about the safety-related aspects of an oCI when compared to the practical aspects. The localized genetic treatment of the inner ear with non-disease-causing viruses was the risk that the highest number of participants were accepting. Patient and public attitudes toward gene and cell therapies is an important topic, as a greater number of gene therapies continue to be explored. In a recent systematic review on patient and public perspectives on gene and cell therapies (Aiyegbusi et al., 2020), it was found that there is a general trend toward positive attitudes and acceptance of these treatment modalities; and this trend increases with the provision of information.

Regarding the practical risks and drawbacks, more than half of participants would accept the hypothetical short-coming of the oCI having higher costs and shorter battery life, respectively. These possibilities were brought to the attention of the participants, as (i) preclinical estimates of energy of pulse requirements of oCI currently exceed those of eCI and (ii) costs of oCI need to accommodate the medical device and gene therapy. Multiple participants brought up battery-life of their current eCI as an issue they would like to improve. This suggests that despite its importance to them, CI users would be more accepting of short battery time if the oCI would be an improvement in the hearing quality they experience. Fewer participants were acceptant to there being no documented human experience with the new CI yet, as clinical trials have yet to be performed. This is not surprising, since the eCI is an ambitious benchmark to surpass (Adel et al., 2019). If there has been no human experience with the oCI, it would be unknown whether it indeed demonstrates superiority to the eCI and addresses the constraints of artificial hearing that CI users must contend with. Thus, we propose that the biggest risk for patients in accepting the new oCI, would be the uncertainty that it would be an improvement to their current implant. Despite this, the majority (89%) of participants indicated that they felt the oCI would be an option for them if it were available today. This could suggest that even though there is no documented human experience, and thus, there is risk that the oCI would not be superior to their current implant, participants are optimistic that the oCI could provide them with improved hearing restoration.

Responses from the open-text section of the questionnaire provides us with valuable insight into what features CI users desire in a new CI, outside of the improvements to the well-documented limitations of artificial hearing. Notably, patients also reported practical considerations (design features, battery life, ease of use) that are of interest for improving current and new CIs–some of which are currently being considered and partially implemented in ongoing CI development ventures (Wolf et al., 2022).

The eCI provides a vital means for hearing rehabilitation in individuals affected by HI, however, the sensory experience of its users remains sub-optimal. Through a survey with current eCI users, we explored their experiences with artificial hearing restoration, and uncovered their preferences and opinions for a new CI. From our results, we found that in our survey population there remains an unmet clinical need in CI users’ hearing experience; and that there is openness for receiving and willingness to collaborate in the development of an oCI. Toward the development of the oCI, we will continue adopt strategies that engages patients in a meaningful way to align their preferences and needs to future research endeavors.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by Ethik-Kommission der Universitätsmedizin Göttingen. The patients/participants provided their written informed consent to participate in this study.

NS and TM: supervision and resources. RK, NS, DK, and TM: conceptualization. RK, NS, VH, and TM: methodology. RK, NS, and TM: investigation. RK and VH: analysis. VH and BW: writing—original draft. All authors: writing—review and editing and approved the submitted version.