Diseases of the Eye and Ear - The ears



The ear, like the eye, is a complicated structure. Its major parts consist of the auditory canal, middle ear, and inner ear. Hearing results from the perception of sound waves whose loud-ness can be measured in decibels and whose highness or lowness of pitch can be measured by their frequency in cycles per second.

Sound waves usually travel through the auditory canal to the eardrum or tympanic membrane , vibrating it in such a way as to carry the vibrations to and along the three interlocking small bones in the middle ear to the inner ear. Here the vibrations are carried to the auditory nerve through a fluid-filled labyrinth called the communicating channel.

An abnormality at any of these points can produce a hearing deficiency. Normal hearing means the ability to hear the spoken voice in a relatively quiet room at a distance of about 18 feet. How well a person hears can be tested by an audiometer, which measures decibels and frequency of sound.

Wax Accumulation

A very common cause of hearing deficiency is the excessive accumulation of wax in the auditory canal, where it is continually being secreted. When the excess that blocks the passage of sound waves is removed—sometimes by professional instrumentation—hearing returns to normal. Anyone whose hearing is temporarily impaired in this way should avoid the use of rigid or pointed objects for cleaning out the accumulated wax.

Ear

Infection

Infections or other diseases of the skin that lines the auditory canal can sometimes cause a kind of local swelling that blocks the canal and interferes with hearing. Although such a condition can be painful, proper treatment, usually with antibiotics, generally results in a complete cure.

A major cause of hearing deficiency acquired after birth is recurrent bacterial infection of the middle ear. The infecting organisms commonly get to the middle ear through the Eustachian tube , which connects the middle ear to the upper throat, or through the eardrum if it has been perforated by injury or by previous infection.

The infection can cause hearing loss, either because it becomes chronic or because the tissues become scarred. Such infections are usually painful, but ever since treatment with antibiotics has become possible, they rarely spread to the mastoid bone as they used to in the past.

Disorders Caused by Pressure

The Eustachian tube usually permits the air pressure on either side of the eardrum to equalize. When the pressure inside the drum is less than that outside—as occurs during descent in an airplane or elevator, or when riding through an underwater tunnel, or during skin diving—the eardrum is pushed inward. This causes a noticeable hearing loss or a stuffy feeling in the ear that subsides as soon as the pressure equalizes again. Yawning or swallowing usually speeds up the return to normal.

When the unequal pressure continues for several days because the Eustachian tube is blocked, fluid begins to collect in the middle ear. This is called serous (or nonsuppurative ) otitis media and can cause permanent hearing damage.

Eustachian tube blockage is more commonly the result of swelling around its nasopharyngeal end because of a throat infection, a cold, or an allergy. Nose drops help to open up the tube, but sometimes it may be necessary to drain the ear through the eardrum or treat the disorder with other surgical procedures.

Otosclerosis

A very common cause of hearing loss that affects about 1 in 200 adults—usually women—is otosclerosis . This disorder is the result of a sort of freezing of the bones in the middle ear caused by an overgrowth of tissue. Only one ear may be involved, but the condition does get progressively worse. Although heredity is an important factor, the specific cause of otosclerosis is unknown. In some cases, surgery can be helpful.

Injury

A blow to the head, or a loud noise close to the ear such as the sound of a gunshot or a jet engine, especially when repeated often, can cause temporary and sometimes permanent hearing defects. Anyone who expects to be exposed to damaging noise should wear protective earmuffs. Injury to the auditory nerve by chemicals or by medicines such as streptomycin can also cause loss of hearing.

Ringing in the Ears

Sometimes people complain of hearing noises unrelated to the reception of sound waves from an outside source. This phenomenon is called tinnitus and occurs in the form of a buzzing, ringing, or hissing sound.

It may be caused by some of the conditions described above and may be relieved by proper treatment. In many cases, however, the cause is unknown and the patient simply has to learn to live with the sounds and ignore them.

Impairment of Balance

The labyrinths of the inner ear are involved not only in hearing but also in controlling postural balance. When the labyrinths are diseased, the result can be a feeling of vertigo or true dizziness. This sensation of being unable to maintain balance is quite different from feeling lightheaded or giddy.

Vertigo can be an incapacitating disorder. Sometimes it is caused by diseases of the central nervous system such as epilepsy or brain hemorrhage, but more often by inflammation sometimes caused by infection of the labyrinth. It can be sudden and recurrent as in Ménière's disease , or somewhat gradual and nonrecurrent. It may or may not be accompanied by vomiting or hearing loss. Treatment for the condition varies depending on the cause.

Deafness

Deafness at birth or in a very young baby is an especially difficult problem because hearing is necessary for the development of speech. Although the deafness itself may be impossible to correct, its early recognition and management can usually prevent muteness from developing.

Many communities now have special schools for deaf children, and new techniques and machines are constantly being devised for helping them to learn how to speak, even if imperfectly. Any doubt about an infant's ability to hear should therefore be brought to a physician's attention immediately.

Deafness at birth can be caused by a maternal infection such as rubella (German measles) during pregnancy. Because children are often the ones who spread this disease, youngsters should be immunized against it.

Hearing Aids

Hearing loss that cannot be treated medically or surgically can often be compensated for by an accurately fitted hearing aid. This device, which now comes in many sizes, shapes, and types, converts sound waves into electrical impulses, amplifies them, and reconverts them into sound waves. A hearing aid can be placed in the auditory canal for air conduction of sound waves, or it can be worn behind the ear for bone conduction. See under “Hearing Loss” in Ch. 6, The Later Years , for further information about hearing aids.



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