Assessment and Preparation
Before being fitted with a hearing aid, patients must undergo an evaluation conducted by an otologist. The evaluation includes otologic examinations and hearing assessments. Otologic examinations help identify hearing loss caused by pathologies of the external auditory canal, tympanic membrane, middle ear, or Eustachian tube. Hearing assessments involve tests such as pure-tone audiometry, tympanometry, and speech audiometry. Pure-tone audiometry and tympanometry assist in determining the type, degree, and frequency range of the hearing loss. Speech audiometry, particularly in a background noise environment, helps evaluate an individual's speech comprehension ability, facilitating predictions about the effectiveness of hearing aids. Additionally, objective audiologic tests such as otoacoustic emission, auditory brainstem response, and multi-frequency auditory steady-state response can further clarify the hearing thresholds of patients with hearing impairment.
Before using hearing aids, active inner ear diseases, as well as conditions of the external auditory canal, tympanic membrane, middle ear, or Eustachian tube, need to be treated first. Once the treatment is complete, patients can consult an audiologist for the fitting of hearing aids.
During the evaluation process for children, it is important to identify and differentiate auditory neuropathy, enlarged vestibular aqueduct syndrome, and other metabolic or genetic syndromes. A comprehensive assessment of developmental delays, as well as a child's auditory and cognitive development, is necessary to obtain precise audiological and medical diagnoses.
Indications for Fitting
Patients with hearing impairment who possess residual hearing and wish to improve their communication abilities can be fitted with hearing aids after completing the evaluation and preparation process, provided their condition is stable.
Air-conduction hearing aids can be used to improve hearing in patients with conductive, sensorineural, or mixed hearing loss. Bone-conduction hearing devices are appropriate for individuals with congenital malformation of the external ear, narrowing or atresia of the external auditory canal, or middle ear malformations, as well as for individuals with recurrent external otitis who cannot tolerate air-conduction hearing aids. They can also be used for patients with unilateral or bilateral conductive or mixed hearing loss, as well as for those with unilateral sensorineural hearing loss.
Fitting Principles
For patients with unilateral hearing loss, hearing aid fitting can be based on individual daily needs. For those with bilateral hearing loss, binaural fitting is generally recommended. However, if financial constraints or other factors limit this option, monaural fitting can be considered. In cases of monaural fitting, the following principles should be observed:
If there is a significant difference in the degree of hearing loss between the two ears, and neither ear's hearing loss exceeds 60 dB, the hearing aid should be fitted to the poorer ear.
If one ear has a hearing loss exceeding 60 dB, the hearing aid should be worn on the better ear.
If the degree of hearing loss is relatively similar in both ears, fitting should prioritize the ear with a higher speech recognition score, a flatter hearing threshold curve, a larger air-bone gap, or a wider dynamic hearing range. Preference should also be given to the dominant ear commonly used in daily life during monaural fitting.