3.5. Provision of hearing aids generally includes the following steps: 1) screening for and diagnosing hearing loss; 2) selecting and fitting appropriate hearing aids; and 3) providing long-term follow-up and rehabilitation services to the user.

FIGURE 2: SAMPLE AUDIOGRAM

Image Description

Sample of an Audiogram. This is a line chart comparing the left and right ear, with hearing levels rated as Normal, Minor hearing loss, Moderate hearing loss, Severe hearing loss and Profound hearing loss. Audiometry uses specialized equipment, called an AudioMeter, to develop an audiogram which describes the hearing loss in terms of volumes (y-axis) across various frequencies (x-axis).

The continuum of care includes the following high-level steps:

1. SCREENING AND DIAGNOSIS. Hearing aid provision begins with case finding and screening for hearing loss or an individual presenting for hearing evaluation. A provider then examines the ear with an otoscope to rule out conductive causes. This is followed by diagnostic testing using audiometry to determine the severity of the hearing loss and if a hearing aid is appropriate. Audiometry uses specialised equipment, called an audiometer, to develop an audiogram (Figure 2), which describes the hearing loss in terms of volumes (y.-axis) across various frequencies (x.-axis).
2. FITTING OF HEARING AID. Once a person has been determined to have hearing loss that can be addressed via a hearing aid and rehabilitation services, the appropriate hearing aid (one that is a good match for severity of hearing loss and takes into account a person's perceptual difficulties) is selected and fitted, whereby a trained professional uses a computer programme to match the audiogram to the appropriate amplification curve of the hearing aid and adjusts based on the user's feedback and potential additional testing. The fitting visit should include fitting, programming, verification, instructions on use, and counselling.
3. REHABILITATION. Rehabilitation services begin at the first fitting when the user is provided guidance and counselling on hearing aid usage. Additional adjustments are made over time to respond to the user's experience. Audiological rehabilitation or peer support may be used to instruct the user in hearing aid management and use as well as on how to adjust to the use of a hearing aid and increase skills related to hearing and speech. This counselling may be carried out in-person or via home-based exercises, e-mail and/or phone calls.
4. AFTER-CARE. Aftercare includes the maintenance and repairs of hearing aids, as well as battery and earmould management. Batteries must be available and replaced regularly, while earmoulds may be replaced every 6-12 months to 3 years depending on age.

Appendix C provides a more detailed description of the hearing aid continuum of care including screening, diagnosis, fitting, and rehabilitation and after-care.

Provision of hearing aids requires earmoulds and batteries over the life of the hearing aid:

• EARMOULDS. Usually made of medical-grade plastic or silicone, earmoulds are custom-made so that they sit comfortably within the user's ear canal, preventing feedback loop, a high-pitched whistling that is caused when the amplified sound leaks out and is re-amplified. The process to develop custom-made earmoulds requires specialised equipment and materials, adding to the supply chain complexity of hearing aids and time required for service provision and fitting. In most places, earmould impressions are sent to a lab where a trained technician develops the mould. This can add additional waiting time and requires follow-up visits to the clinic, which may limit access. Furthermore, earmoulds typically last 2-3 years for adults and 6-12 months among children and hence need to be made consistently available to ensure long-term usage. The medical-grade silicone or plastic is often unavailable locally and must be imported. Experts suggest that earmoulds in L.M.I.C.s cost ~U.S.$5-8.

• EARDOMES. Many experts suggest the use of eardomes instead of earmoulds as a way to increase access, as they are factory made and do not require customisation (refer to Figure 3); however, they cannot be used for all users due to acoustic ventilation that can cause negative feedback loop or loss of amplification. Eardomes come in multiple sizes and the user can pick the one that is most comfortable. The cost of these eardomes is significantly lower than a custom earmould (< U.S.$0.10).34

  FIGURE 3: EARMOULDS AND EARDOMES

  Earmoulds	Eardomes

• BATTERIES. Access to a continuous supply of batteries is critical to ensure continued use as hearing aid batteries deplete on average every 5-10 days depending on the processing power and features of the hearing aid. Sizes of hearing aid batteries are developed for and unique to hearing aids; therefore, they are often not locally available in L.M.I.C.s. Hearing aid batteries cost between U.S.$0.17 – U.S.$0.38 per battery across both L.M.I.C. and H.I.C. markets, which translates to about U.S.$12 – U.S.$50 per year in battery costs depending on depletion rate. Experts suggest that rechargeable batteries are far more cost-prohibitive at the moment and make limited sense for hearing aids that must be worn for the majority of the day.