CHAPTER ONE-- CONDITIONS of the EYE 1-16
Retinitis Pigmentosa 1-5 Glaucoma 5-8 Diabetic Retinopathy 8-12 Cataracts 12-15 Summary & Implications 16
CHAPTER TWO-- CONDITIONS of the EAR 17-31
Conductive Hearing Loss 24-25 Sensori-Neural Hearing Loss 25-28 Mixed Hearing Loss 29-30 Summary & Implications 31
CHAPTER THREE-- METHODS OF COMMUNICATION 32-49
Non-manual 32-42 Manual 42-49
CHAPTER FOUR-- HABILITATION & REHABILITATION 50-57
Simple Adaptations 51-52 Specialized Equipment 52-55 Etiquette Techniques 55-57
Answers to Quiz & Explanations Illustration of the Eye List of References
|Conditions of the Ear|
|Conductive Hearing Loss
Sensori-neural Hearing Loss
Mixed Hearing Loss
Summary & Implications
A hearing loss can occur in any part or combination of parts of the ear. There are three divisions. First, there is the outer ear consisting of cartilage, ear canal, and ear drum responsible for funneling sound into the ear. Second, the middle ear consists of three boney structures called the hammer, anvil, and stapes responsible for conducting sound waves to the inner ear. Third, the inner ear consists of three complex elements. There are the semi-circular canals responsible for our sense of balance and movement. The cochlea, a snail-shaped boney structure with hair cells and fluid inside, is responsible for converting sound waves from the middle ear into electrical impulses. and It is the auditory nerve which receives these impulses and relays the message to the brain. The brain is responsible for interpreting the message (see figure 2.1).
The brain learns to interpret the messages we perceive through our organ of hearing. For example, if you close your eyes right now and quietly listen to what is going on around you, you may hear a dog barking or someone rustling papers. You do not need to see the dog to know s(he) is there; you can hear. You learned as a small child that barking sounds come from a dog. You have learned what rustling paper sounds like. If you hear a new sound, your brain will quickly search for a vocabulary to describe it. More than likely you will feel uncomfortable until you seek the source of the sound and identify it for yourself. Your brain has learned how to interpret a new sound and will file that new message for later reference if needed.
In order to discuss degrees of hearing loss and types of hearing loss, you must first familiarize yourself with an audiogram and the terminology we will use in this chapter.
An audiogram is simply a graph on which an individual's responses to the hearing test are plotted. The verticle lines represent the frequencies from low to high pitch recorded in hertz (125Hz-8000Hz). The horizontal lines represent the loudness levels from very soft to very loud recorded in decibels (0dB-120dB). The level of hearing loss, ie. 50dB or 26dB, is obtained by averaging the hearing level recorded on 500 Hz, 1000Hz, and 2000Hz (see figure 2.2).
When an individual is undergoing a hearing test, s(he) will be tested by air conduction with headphones and bone conduction with a bone conduction vibrator. If the air conduction test shows normal hearing in the individual, then a bone conduction test will not be necessary because the hearing is normal. A hearing test will determine whether the individual has normal hearing, conductive hearing loss, sensori-neural hearing loss, or a mixed loss. The individual's responses are based on when s(he) first hears the sound. The audiologist then records the response on the audiogram.
An audiologist uses symbols to record the responses. The air conduction symbol for the right ear is an "o". The symbol for the left ear is an "x". Bone conduction responses are symbolized by "<" for the right ear and ">" for the left ear (see figure 2.3).
What is air conduction and bone conduction? There are two ways that sound can be conveyed to the inner ear. One way is by air conduction. In this case sound waves enter the outer ear. These sound waves set off a chain of vibrations of the bones of the middle ear which in turn conduct sound into the inner ear.
Another way of conducting sound to the inner ear is through bone conduction. The inner ear is encased in bone. When this bone is vibrated, the fluid in the inner ear is set into motion. The hair cells begin to move. Electrical impulses are sent to the brain via the auditory nerve and is interpreted. To demonstrate this process, plug your ears with your fingers. Now talk. If you have normal hearing, you will be able to hear and understand what you say.
The difficulty with hearing outside stimulus through bone conduction is that the stimulus has to be fairly loud to be heard. Listen quietly for a moment. Now plug your ears again. The ambient sounds are no longer audible to you. You will probably hear blood pulsating, your heart beating, and perhaps your joints creaking. You will not hear wind or quiet traffic. Persons with normal hearing are able to utilize both air and bone conduction and can interpret what they hear.
Now, let us discuss degrees of loss. There are degrees of loss ranging from mild to profound. Hearing is measured in decibels, which is the degree of loudness required to hear the sound.
Normal hearing falls within a range of 0dB to 26dB. A person with normal hearing is able to hear and understand all speech sounds and environmental sounds.
A mild hearing loss is between 27dB and 40dB. A person with a mild loss experiences difficulty hearing faint speech and understanding speech at a normal loudness if there is noise in the background, ie. air conditioner, talking, traffic, etc.
A moderate loss falls between 4ldB to 55dB. This person experiences difficulty in the same areas that someone with a mild loss experiences. Also, s(he) will experience difficulty understanding conversational speech at normal loudness levels even if there are no background noise. It is at this point that some use of lipreading becomes helpful.
A moderately severe loss is between 56dB and 70dB. A person with this degree of loss will be asking for things to be repeated. S(he) will most likely shy away from social functions because of the difficulty experienced in understanding speech even at loud levels. The person's own speech may be affected. The individual would definitely benefit from amplification.
A severe loss falls within 71dB and 90dB or worse. This person will only hear speech if it is amplified and will likely misunderstand spoken conversation. Her/his own speech will likely show defects.
Finally, a profound hearing loss is 90dB or worse. This person may hear but will not understand even amplified speech. Many times amplification is used so the person can hear danger signals ie. warning sirens. Still, that is the extent of its use.
The level of a visual and hearing-impaired person's functioning will depend on a combination of the visual impairment, hearing impairment, and mental capacity. For example, someone who is visually-impaired, but not legally blind, may function as a blind person because of the hearing impairment and mental capacity. S(he) may not hear or process information well enough to accommodate for the vision loss and will need to be helped as if s(he) were legally blind. Or a person may have a mild to moderate hearing loss but, because of the severity of the visual impairment, this person may function as a hard-of-hearing person and will benefit from amplification. Each case must be considered individually given the complexity of the dual impairments.
Now that you have a better understanding of the levels of hearing loss, let us now take into consideration the types of loss. Most people feel that if a person has a hearing impairment s(he) can be helped by the use of a hearing aid. Unfortunately, this is not always the case. Many a frustrated adult has battled with an elderly parent about why the parent does not keep her/his hearing aids on and/or why s(he) cannot hear even when the hearing aids are on.
Many bewildered parents of hearing-impaired children wonder why their sons and daughters still have distorted speech even though they wear the hearing aids and have had extensive speech therapy. Often people are confused when a family member or friend who is wearing hearing aids can hear them at one time but not the next. Often feelings of confusion, anger, and even resentment arise because you feel the hearing-impaired person is ignoring you or not "trying to understand" what you are saying. The hearing-impaired person is also frustrated because it is exhausting trying to overcome a hearing deficit and s(he) too may be expecting more out of the hearing aids than is possible. The hearing-impaired person may accuse you of mumbling or of not speaking loudly enough. Because of confinement to the written word here, visual illustrations of the various losses will be made to give you a better understanding of what the hearing-impaired person hears.
There are three types of hearing losses: conductive, sensori-neural, and mixed. As with the eye conditions discussed in chapter one, each type of hearing loss has its own characteristics to consider. Coupled with a visual impairment, any of these types of hearing losses can significantly impair an individual's functioning.
A conductive hearing loss is a dysfunction of the outer or middle ear with normal hearing capacity in the inner ear. In other words the outer or middle ear fails to "conduct" sound to the inner ear. The cartilage may be deformed and does not funnel sound into the ear. The ear canal may be blocked by wax or infection. The bones in the middle ear may not work properly because of age or injury, or the middle ear may be filled with fluid.
A person with a conductive loss may tend to speak quietly because s(he) can hear her/himself very well. This person may be unaware of ambient noise in the environment so will not adjust her/his level of loudness for others to be able to hear her/him.
For example, a client has a 40dB conductive hearing loss (see figure 2.4). This individual will not be able to hear any of the sounds above the line. That means this particular individual will not be able to hear: z, v, sh, ch, p, h, g, k, f, s, and th. How will this sound? Try reading this short paragraph out loud. Remember these sounds are missing; try not to fill them in when reading:
e mo ing ing a a a ened i a ye r i e bir o my dau er. A new baby ee me bu bu er a nly i or i .
Not very understandable is it? This is what the paragraph actually says:
The most exciting thing that has happened this past year is the birth of my daughter. A new baby keeps me busy but it certainly is worth it.
Depending on the cause of the conductive loss, surgery may be performed and normal hearing restored. If surgery is not possible, amplification may be used.
A sensori-neural hearing loss is a dysfunction of the inner ear or nerve pathway to the brain. It may be the hair cells in the cochlea are damaged, or there may be a tumor on the auditory nerve. With the advent of cochlear implants, some people, who have a damaged cochlea but have normal nerve function, have been helped with this type of surgery. Unfortunately, normal hearing can never be achieved.
A person with a sensori-neural loss is not able to hear her/himself clearly, nor is s(he) able to hear others clearly. Often a person with a sensori-neural hearing loss has described her/his hearing as sounding like a radio station which is not quite tuned in. In other words, s(he) may hear static or other types of interference, and the incoming message will be unclear.
An individual with a sensori-neural hearing loss may speak too loudly. Even though s(he) cannot hear her/himself clearly, s(he) may attempt to speak loudly enough to perceive her/his own voice. Often the individual learns to adjust her/his voice level to the appropriate loudness level by being sensitive to the listener's reactions. S(he) will notice whether s(he) is speaking too softly because the listener is straining to hear. If s(he) is speaking too loudly, the listener is grimacing.
Sensori-neural hearing losses vary. Generally the loss shows good to fair hearing in the low and mid frequencies with poor hearing in the higher frequencies. An individual may even show normal or close to normal hearing in the 500Hz-2000Hz range but drop off sharply after 2000Hz (see figure 2.5). If you recall I mentioned earlier that the hearing level is obtained by figuring the average of the individual's responses at 500Hz, 1000Hz, and 2000Hz. An individual with this pattern of loss can "hear" at normal loudness but not necessarily understand what is being said. The confusion stems from the ability to understand only parts of the words spoken. for example, the individual will not be able to hear the difference between kick, thick, and sick and will only hear the i sound in these words.
Speaking louder to a person with a sensori-neural hearing loss of this pattern will only cause more distortion. S(he) can hear your voice. The problem is in understanding what you are saying. Speaking slowly and enunciating are more effective ways of communicating. There is no need to exaggerate the words.
Individuals with a sensori-neural hearing impairment do not hear well when there is noise in the environment, ie. air conditioner, television, other people talking, traffic, etc. The ambient sounds add to the distortion of conversational speech. This reaction is in contrast to a conductive impairment where the individual may not even be aware of the ambient noise.
It is difficult to simulate the distortion of a sensori-neural hearing loss in print form. However, the same paragraph used above may serve as an example. Keeping this paragraph in mind, imagine radio distortion added to the loss of speech sounds. In this example the sensori-neural loss will be at 10dB with a sharp drop at 2000Hz. Remember the average would make the loss appear within the normal range, but look what happens:
e mo e ing ing a as appened i year is e bir of my dau er. A new baby eeps me busy bu i er ainly is wor i .
This is normal hearing level? Yes! Pretty confusing paragraph isn't it? Add distortion to the sounds heard, and you can imagine the difficulty understanding a normal conversation.
There is no real cure for a sensori-neural hearing loss. However, new technology has allowed an individual with a damaged cochlea to have some hearing restored by undergoing surgery for a cochlear implant. Cochlear implant surgery can only help those individuals who have damage to the cochlea only. If there is damage to the nerve pathway to the brain, then the surgery will not be performed. Hearing aids can help some individuals, but, as you can see from the above example, normal conversation can continue to be confusing.
A mixed hearing loss is a combination of a conductive hearing loss and a sensori-neural hearing loss. A mixed hearing loss is a dysfunction of the outer and/or middle ear and the inner ear. A mixed loss may be caused by osteosclerosis (hardening of the bones in the middle ear) and some damage to the cochlea because of age or noise induced hearing loss.
A mixed hearing loss manifests in a variety of patterns. Like the conductive and sensori-neural hearing losses, a mixed loss can be mild. Still, there must be a 15dB difference between the conductive component and the sensori-neural component (see figure 2.6).
An individual with this type of loss will experience the symptoms of both losses. S(he) may respond to a 500Hz tone at 30dB bone conduction but may not hear the same tone by air conduction until 45dB. S(he) will still hear her/himself better than outside conversation but neither will be very understandable. S(he) may still speak too loudly or too softly than necessary and will have difficulty understanding normal conversational speech.
For example, the illustration below shows a mixed hearing loss with a 30dB conductive component and a 45dB sensori-neural component. The mixed loss will sound like this (don't forget to imagine distortion for the sensori-neural component):
e e ye o au e. ew y ee e u e y o .
Because of the conductive component when this individual speaks, s(he) will be able to hear her/himself make the following speech sounds: ch, sh, j, m, d, b, i, o, a, r, ng, e, l, and u.
An individual with a mixed hearing loss may or may not be helped by the use of hearing aids. The prognosis primarily depends on the cause of the mixed loss and the degree of the loss.
Imagine having any one of the aforementioned hearing losses and couple it with a visual impairment. As I mentioned earlier in this chapter, an individual's level of functioning will depend on the type and degree of hearing loss, type, severity of the visual impairment, and mental capacity. Now, you may have a better understanding of how an individual with a mild sensori-neural hearing loss may function as a severely hard-of-hearing person when her/his visual impairment does not allow the individual to lip read.
When an individual experiences both a visual impairment and a hearing impairment, the dual handicap can be devastating to her/his life. Physical, psychological, and emotional barriers must be overcome. It would greatly benefit the individual to participate in a rehabilitation program for the visually impaired which would also incorporate aspects of rehabilitation with the hearing impaired. The individual should consult with a certified audiologist and an onto laryngologist (ear, nose, and throat specialist). These professionals are able to diagnose the severity and type of hearing loss and will determine if surgery or hearing aids would be required. They also take into consideration the visual impairment when preparing a rehabilitation program.