Spectacle Hearing Aids Explained

A fair number of people ask us whether we supply spectacle hearing aids; perhaps because Jamie Murray Wells, the founder of GlassesDirect, is also HearingDirect’s chairman. I guess it would seem like a neat link up between the companies! Whatever the reason for the contact, it is apparent that there is a great deal of interest in this particular hearing solution, and I hope the following will be a source of information for those searching for further explanation. As the name implies, spectacle hearing aids are hearing aids integrated into the frames/arms of a pair of glasses. Spectacle hearing aids are most commonly associated with ‘bone conduction’ fittings, but some ‘air conduction’ spectacle hearing aids are also available. If the terms ‘bone’ and ‘air’ conduction need further explanation, a quick anatomy and physiology lesson is required. The ear can be divided into three parts: the outer ear (which is everything outside up to the eardrum); the middle ear (an air-filled cavity containing the three tiniest bones in the human body) and then the inner ear (where sound is converted to neural impulses to be sent up the auditory nerve for further interpretation in the brain). Sound passing through all three of these areas is said to be transmitted via air conduction. Our inner ear can however also be stimulated directly from vibrations in the skull – this is referred to as bone conduction. Bone conduction tests are performed as part of a standard hearing test, to rule out whether a hearing loss is related to problems in the middle or outer ear. Some conditions such as a wax build up in the ear canal, or a disease of the ossicles will mean that a person will hear sounds presented via a vibrator on the mastoid bone (the section of the skull directly behind the ear) better than the same sound presented through headphones. So, back to spectacle hearing aids: bone conduction spectacle hearing aids may therefore be used if the inner ear is completely or nearly intact, but a hearing loss is present due to a problem in the middle ear and/or the ear canal. Sound is picked up via a microphone in the glasses frames and the amplified output is delivered to a vibrator component which lies against the mastoid bone. Contrary to how much these spectacle hearing aids seem to be advertised, many hearing healthcare professionals will only consider fitting these if the condition of the outer ear/middle ear does not permit the use of a conventional hearing aid. Some of these conditions are as follows:

• Severe skin problems in the ear canal (e.g. eczema)
• A radical operation on the middle ear has been performed
• Chronic otitis media (discharge)
• The ear canal is closed or extremely narrowed (stenosis)

In the above cases a well-fitted bone conduction spectacle aid does offer the possibility of a successful outcome. As the transmission of the vibrations is crucial; the fit of these spectacles must be right; and can be difficult to achieve - one of the reasons why HearingDirect do not offer spectacle aids as online purchases. Air conduction spectacle hearing aids are also available, where the sound is delivered into the ear canal; through the use of an earmould. The only difference compared to a more traditional behind-the-ear hearing aid is that the hearing aid components are built into the frame of the glasses. For people who wear glasses already, these can appear like ideal solutions, particularly in bone conduction spectacles where nothing is put into the ear canal. It is however worth bearing in mind that this ‘combination’ device does mean that when one’s glasses are removed for any reason, amplification is removed as well. And, any faults with the hearing aid or lenses, may mean losing out on improved hearing/vision at the same time.