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vative estimate, approximately 1% of the people who could benefit from a CI has received one.
I think a population health perspective would be helpful in increasing the access; progress already has been made along these lines (Zeng, 2017). Access is limited by the cost of the device but also by the availability of trained medical person- nel; the infrastructure for healthcare in a region or country; awareness of the benefits of the CI at the policy levels such as the Ministries of Finance and Ministries of Health; the cost of surgery and follow-up care; additional costs associated with the care for patients in remote regions far from tertiary-care hospitals; battery expenses; the cost for manufacturers in meeting regulatory requirements; the cost for manufacturers in supporting clinics; the cost of marketing where needed; and the cost of at least minimal profits to sustain manufac- turing enterprises. Access might be increased by viewing it as a multifaceted problem that includes all of these factors and not just the cost of the device, although that is certainly important (Emmett et al., 2015).
Efforts are underway by Ingeborg J. Hochmair and me and by Fan-Gang Zeng and others to increase access. We know that even under the present conditions, CIs are cost effec- tive or highly cost effective in high- and middle-income countries and are cost effective or approaching cost effective- ness in some of the lower income countries with improving economies (Emmett et al., 2015, 2016; Saunders et al., 2015). However, much more could be done to increase access—es- pecially in the middle- and low-income countries—so that “All may hear,” as Bill House put it years ago, and as was the motto for the House Ear Institute in Los Angeles (founded by Bill's half brother Howard) before its demise in 2013 (Shan- non, 2015).
Improving Unilateral Cochlear Implants
As seen in Figure 3 and as noted by Lim et al. (2017) and Zeng (2017), the performance of unilateral CIs has been relatively static since the mid-1990s despite many well-conceived efforts to improve them and despite (1) multiple relaxations in the candidacy criteria for cochlear implantation; (2) increases in the number of stimulus sites in the cochlea; and (3) the advent of multiple new devices and processing strategies. Presumably, today’s recipients have healthier cochleas and certainly a high- er number of good processing options than the recipients of the mid-1990s. In the mid-1990s, the candidacy criteria were akin to “can you hear a jet engine 3 meters away from you?” and, if not, you could be a candidate. Today, persons with sub- stantial residual hearing, and even persons with a severe or
worse loss in hearing one side but normal or nearly normal hearing on the other side, can be candidates for receiving a CI.
These efforts and differences did not move the needle in the clockwise direction. New approaches are obviously needed, and some of the possibilities are presented by Wilson (2015, 2018), Zeng (2017), and Wilson and Dorman (2018b); one of those possibilities is to pay more attention to the “hearing brain” in designs and applications of CIs.
Better performance with unilateral CIs is important because not all patients or prospective patients have access to, or could benefit from, the adjunctive stimulation treatments. In particular, not all patients have enough residual hearing in either ear to benefit from combined EAS (Dorman et al., 2015), even with the relaxations in the candidacy criteria, and not all patients have access to bilateral CIs due to re- strictions in insurance coverage or national health policies. Furthermore, the performance of the unilateral CI is the foundation of the adjunctive treatments and an increase in performance for unilateral CIs would be expected to boost the performance of the adjunctive treatments as well.
Broadening Eligibility and Indications
Even a slight further relaxation in the candidacy criteria, based on data, would increase substantially the number of persons who could benefit from a CI. Evidence for a broadening of eli- gibility is available today (Gifford et al., 2010; Wilson, 2012).
An immensely large population of persons who would be in- cluded as candidates with the slight relaxation are the sufferers of presbycusis, which is a socially isolating and otherwise debili- tating condition. There are more than 10 million people in the United States alone who have this affliction, and the numbers in the United States and worldwide are growing exponentially with the ongoing increases in and aging of the world’s populations. A hearing aid often is not effective for presbycusis sufferers be- cause most of them have good or even normal hearing at low frequencies (below about 1.5 kHz) but poor or extremely poor hearing at the higher frequencies (Dubno et al., 2013). The am- plification provided by a hearing aid is generally not needed at the low frequencies and is generally not effective (or only mar- ginally effective) at the high frequencies because little remains that can be stimulated acoustically there. A better treatment is needed. Possibly, a shallowly and gently inserted CI could pro- vide a “light tonotopic touch” at the basal (high-frequency) end of the cochlea to complement the low-frequency hearing that already exists for this stunningly large population of potential beneficiaries.
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