4.1 Comparison with the existing literature
In South Korea, the NHIS covers only one hearing aid for hearing-disabled patients registered with the Ministry of Health and Welfare, who can but the other hearing aid at their own expense. So, we often encounter a lot of patients who can buy only one hearing aid. For monaural amplification in AHL, two questions are useful in selecting the ear to be aided. (1) If the better ear is aided, can aided hearing improve audibility as well as communication for the AHL patient? (2) If the worse ear is aided, can aided hearing make a patient understand speech better in quiet as well as in noise and provide advantages of binaural hearing? Empirically, UHL seems to be suitable for monaural amplification but AHL1 is likely to be a candidate for binaural amplification. AHL2 seems to be a dilemma for selection which ear to amplify monaurally; if worse ear is amplified, binaural symmetry can be accomplished but both hearing is more likely to be handicapped. If better ear is amplified, the patient may get only one serviceable hearing. In the AHL1 and AHL2 subtypes defined in this study, these two questions should be considered together, but only the second question is relevant to patients with UHL or SSD. The 60 dB HL rule or Briskey’s criteria for successful binaural fitting are not enough to offer a reasonable solution.12