Age-Related Hearing Loss : Hearing Aids

by Food and Drug Administration (FDA)

(Page 3 of 4)

Hearing aids are tiny instruments worn in or behind the ear that amplify sounds in people with either conductive or sensorineural hearing loss. Some need a hearing aid for only one ear. Others need one for both. A health care professional will determine whether you need one or two.

Hearing aids have different electronic characteristics that are chosen to suit the person's particular type of hearing loss. For example, people whose hearing loss affects mainly higher frequencies do not benefit from simple amplification, which merely makes the mumbled speech they hear sound louder. Hearing aids that selectively amplify the high frequencies markedly improve speech recognition. Other hearing aids contain vents in the ear mold — a specially molded piece of Lucite or vinyl material that fits inside the device — which facilitate the passage of high-frequency sound waves into the ear.

Staecker says different hearing losses respond differently to treatment with hearing aids. He describes people's hearing as similar to listening to a radio. "Certain hearing losses are like having the volume knob on the radio turned down. When you increase the volume on your radio from very low to audible, information is heard more clearly," he says. "In other losses there is a volume problem and a reception problem. If the station you are listening to is not tuned in clearly, no matter how much you increase the volume, the information coming from the radio will not be clear." These types of hearing losses, he adds, do not necessarily respond well to hearing aids.

Many hearing aids use digital sound processing with multiple frequency channels so that the amplification can even more precisely match the person's hearing loss. But Eric A. Mann, M.D., Ph.D., chief of the FDA's Ear, Nose, and Throat Devices Branch, says that some of these devices may not be suitable for older people, who might find it difficult to manage the small, often complex components. People who cannot tolerate loud sounds may need hearing aids with special electronic circuitry that limits the maximum volume of sound to a tolerable level.

Here are some of the most common types of hearing aids and their advantages and disadvantages:

Behind-the-ear: carries sound to the ear through a custom ear mold. These devices are useful for mild-to-severe hearing loss. Hearing aids attached to eyeglasses are a type of behind-the-ear hearing aid.

In-the-ear: custom-made to fit in the outer ear. These devices are useful for mild to severe hearing loss. No outside wires are visible because they are inside the device.

In-the-ear-canal: custom-made to fit in the ear canal. These aids help people with all but the worst hearing loss. There are no outside wires or tubes, and these devices are almost impossible to see. This device is relatively inconspicuous but is difficult to use with telephones.

On-the-body: includes a case with a larger microphone, amplifier, and battery. These devices are for people with significant hearing loss. The case can be carried in pockets or attached to clothing, and is connected by a wire to an ear receiver that is attached to an ear mold.

People who sell, lease, or rent hearing aids have certain obligations to their customers. Federal rules require that people visit a doctor to rule out a medical problem before being fitted for hearing aids by a licensed hearing aid dispenser. The FDA does allow people to buy hearing aids without a medical exam — for example, because of religion or personal beliefs — if they sign a waiver provided by the hearing health care specialist at the time of the purchase. Dispensers should not encourage people to waive their right to a medical exam, however, and must advise them that it is not in their best interest to do so.

In practice, Mann says that many people waive the requirement. The result, like for McKinney, is that they are not properly evaluated and fitted before they buy and use hearing aids. "Unfortunately, consumers may fail to have diagnosed a medically treatable cause for their hearing loss — something as simple as a wax buildup or as serious as a tumor of the hearing nerve," he says.

Hearing aids sold through the mail must also meet FDA regulations. Kane, who reviews hearing aid devices at the FDA, advises people to adopt a "buyer beware" posture. He says that it's important for people to have a medical clearance before buying a hearing aid through the Internet. "It makes sense. A doctor's referral will help people find a certified, legitimate hearing aid dispenser that they can rely on."

Kane also says that "auditory rehabilitation is more than just purchasing a hearing aid." Appropriate counseling from a professional is critical for success with amplification. "Purchasing over the Internet precludes this important rehabilitation component," he says. The patient's spouse and family members also need to be counseled about the expected limitations and the benefits, because they are a part of the person's communication environment.

Prices of hearing aids vary considerably, depending on the technology. Staecker, who regularly refers people for hearing aids, says to get a second opinion when comparing the price and features of hearing aids.

As for mobile phones, laboratory testing of more than 20 hearing aid models found that those tested were susceptible to interference from the digital cellular phones that are now used in the United States. In general, behind-the-ear hearing aids experienced higher levels of interference than in-the-ear devices. Currently, a testing standard is being developed that will allow consumers to see ratings of the "compatibility" of specific combinations of mobile phone and hearing aid models. People should ask their dispensers for more information on mobile phone use and the type of hearing aid they are interested in.

Mann adds that the Federal Communications Commission has recently required that wireless phone manufacturers and wireless service carriers must make digital wireless phones compatible with hearing aids within the next five years.

It may take several weeks or months for a person to learn to interpret the new sounds from a hearing aid, and there is great variability in the results. Many hearing aid manufacturers offer trial rental or purchase option plans — usually up to 30 days — to allow their customers to judge the product's effectiveness and benefits. Check with your state health department to find out about the regulations covering trial periods for hearing aids. Kane says that some states have special licensing divisions within the larger health department.

People with severe to profound hearing loss who aren't helped by hearing aids may benefit from a cochlear implant. This is an electronic hearing device that is surgically implanted behind the ear, with wires and electrodes inserted into the cochlea and a microphone and transmitter that are worn outside the body. It is designed to produce useful hearing sensations by electrically simulating nerves inside the inner ear. Although a cochlear implant can't restore normal hearing, it can help a person hear sounds and distinguish between them.

Implantable middle ear hearing devices are designed to restore some hearing by vibrating the tiny bones of the middle ear in people with mild to moderately severe sensorineural hearing loss. The person must have a healthy middle ear, but may opt for an implant simply because they do not want to use conventional hearing aids. The advantage of this device over a conventional hearing aid is that it is not dependent on simply amplifying sound, as is a hearing aid.

Auditory brainstem implants are intended to restore useful hearing in people who experience total hearing loss when the removal of tumors damages their cranial hearing nerves. The device restores the ability to detect certain sounds and speech, although it does not restore normal hearing. It is surgically implanted into the brain and electrically stimulates the area that normally receives the electrical signal from the ear. The patient wears a pocket-sized speech processor that picks up sound and changes it into electrical pulses that are transmitted to the implant.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.