Chapter 13: Sensory Disabilities - Hearing and Vision Loss

Audition

act or sense of hearing

auditory process

involves the transmission of sound through the vibration of an object to a receiver.

deaf and hard of hearing (or partial hearing)

commonly used to indicate the severity of a person’s hearing loss.

0 dB to 130 dB

range of human hearing

Hertz (Hz)

A unit used to measure the frequency of sound in terms of the number of cycles that vibrating molecules complete per second

Deafness

A hearing loss greater than 90 dB. Individuals who are deaf have vision as their primary input and cannot understand speech through the ear.

Hard of hearing

A sense of hearing that is deficient but somewhat functional.

Prelingual loss

Pertaining to hearing impairments occurring prior to the age of 2, or the time of speech development.

Postlingual loss

Pertaining to hearing impairments occurring at any age following speech development.

Conductive hearing loss

A hearing loss resulting from poor conduction of sound along the passages leading to the sense organ.

Sensorineural hearing loss

A hearing loss resulting from an abnormal sense organ (inner ear) and a damaged auditory nerve.

Mixed hearing loss

A hearing loss resulting from a combination of conductive and sensorineural problems

Visual cortex

The visual center of the brain, located in the occipital lobe.

Optic nerve

The nerve that connects the eye to the visual center of the brain.

Cornea

The external covering of the eye.

Pupil

The expandable opening in the iris of the eye.

Iris

The colored part of the eye that controls the size of the pupil and regulates the amount of light entering the eye.

Lens

The clear structure of the eye that bends light rays so they strike the retina directly

Retina

Light-sensitive cells in the interior of the eye that transmit images to the brain via the optic nerve.

Blind

Condition in which central visual acuity does not exceed 20/200 in the better eye with correcting lenses, or in which visual acuity, if better than 20/200, is limited in the central field of vision.

vision loss

encompasses people with a wide range of conditions, including those who have never experienced sight, those who had normal vision prior to becoming partially or totally blind, those who experienced a gradual or sudden loss of acuity across their field of vision, and those with a restricted field of vision

Legal blindness

Visual acuity of 20/200 or worse in the best eye with best correction as measured on the Snellen test, or a visual field of 20 percent or less

Visual acuity

Sharpness or clearness of vision

Snellen test

by using an index that refers to the distance from which an object can be recognized. People with normal eyesight are defined as having 20/20 vision.

Tunnel vision

A restricted field of vision that is 20 degrees or less at its widest angle

Partially sighted

Visual acuity greater than 20/200 but not greater than 20/70 in the better eye after correction.

Braille

A writing system for the blind that involves combinations of six raised dots punched into paper, which can be read with the fingertips.

Refractive problems

Visual disorders that occur when the refractive structures of the eye fail to properly focus light rays on the retina.

Hyperopia

Farsightedness; a refractive problem wherein the eyeball is excessively short, focusing light rays behind the retina.

Myopia

Nearsightedness; a refractive problem wherein the eyeball is excessively long, focusing light in front of the retina.

Astigmatism

A refractive problem that occurs when the cornea surface is uneven or structurally defective, preventing light rays from converging at one point.

Cataract

A clouding of the eye lens, which becomes opaque, resulting in visual problems.

Muscular defects of the visual system

occur when one or more of the major muscles within the eye are weakened in function, resulting in a loss of control and an inability to maintain tension

Nystagmus

Uncontrolled rapid eye movements.

Strabismus

Crossed eyes (internal) or eyes that look outward (external).

Amblyopia

Loss of vision due to an imbalance of eye muscles.

Esotropia

A form of strabismus causing the eyes to be pulled inward toward the nose.

Exotropia

A form of strabismus in which the eyes are pulled outward toward the ears.

Receptive Eye Problems

Disorders associated with the receptive structures of the eye occur when there is a degeneration of or damage to the retina and the optic nerve

Optic atrophy

A degenerative disease caused by deteriorating nerve fibers connecting the retina to the brain.

Retinitis pigmentosa

A hereditary condition resulting from a break in the choroid.

Retinal detachment

A condition that occurs when the retina is separated from the choroid and sclera.

Retinopathy of prematurity (ROP)

• occurs when too much oxygen is administered to premature infants, resulting in the formation of scar tissue behind the lens of the eye, which prevents light rays from reaching the retina.

• A term now used in place of retrolental fibroplasia.

Deaf culture

A culture where people who are deaf become bonded together by a common language (sign language), customs, and heritage, and rely on each other for social interaction and emotional support.

Verbalisms

Excessive use of speech (wordiness) in which individuals use words that have little meaning to them.

Otosclerosis

A disease of the ear characterized by destruction of the capsular bone in the middle ear and the growth of a weblike bone that attaches to the stapes. The stapes is restricted and unable to function properly.

Tinnitus

High-pitched throbbing or ringing sounds in the ear, associated with disease of the inner ear

Congenital cytomegalovirus (CMV)

Viral infection that spreads by close contact with another person who is shedding the virus in body secretions.

Congenital toxoplasmosis infection

Characterized by jaundice and anemia, this disease frequently results in central nervous system disorders.

Hydrocephalus

Condition resulting in excess cerebrospinal fluid in the brain.

Atresia

The absence of a normal opening or cavity.

Otitis media

An inflammation of the middle ear.This condition can result in fluid buildup, ear pain, and fever.

Albinism

Lack of pigmentation in eyes, skin, and hair

Photophobia

An intolerance to light.

Retinoblastoma

A malignant tumor in the retina.

Microphthalmia

An abnormally small eyeball.

Anophthalmia

Absence of the eyeball.

Glaucoma

A disorder of the eye, which is characterized by high pressure inside the eyeball.

Buphthalmos

An abnormal distention and enlargement of the eyeball.

Xerophthalmia

Vitamin A deficiency that can lead to a lack of mucous-producing cells (known as dry eye) or blindness.

Cortical visual impairment (CVI)

A leading cause of acquired blindness, which involves damage to the occipital lobes and/or the visual pathways to the brain, resulting from severe trauma, infections, or drug abuse.

Trachoma

Infectious bacterial disease associated with poor living standards and inadequate hygiene. Leads to blindness due to repeated infections causing irritation and scars on the eyelids.

Macular degeneration

An age-related condition in which the macula (tissues within the retina) break down, resulting in distorted and blurred central vision.

Otologist

Specialist involved in the study of the ear and its diseases.

Cochlear implant

Procedure that implants an electronic device under the skin behind the ear to directly stimulate the auditory nerve.

Audiologist

A specialist in the assessment of a person’s hearing ability.

Epiphora

An overflow of tears from obstruction of the lachrymal ducts of the eye.

Speech-reading

The process of understanding another person’s speech by watching lip movement and facial and body gestures.

Sign languages

Complex combinations of hand movements that communicate whole words and complete thoughts rather than the individual letters of the alphabet.

American Sign Language (ASL)

A type of sign language commonly used by people with hearing impairments. ASL signs represent concepts rather than single words.

Sign systems

Differing from sign languages, sign systems create visual equivalents of oral language through manual gestures. For example, finger spelling uses a separate sign for each letter of the English alphabet.

Bicultural–bilingual approach

Instructional approach advocating ASL as the primary language and English as the second language for students who are deaf.

Total communication

A communication approach that uses elements from manual, oral, and any other techniques available to facilitate understanding.

Cued speech

facilitates the development of oral communication by combining eight hand signals in four different locations near the person’s chin.

Closed-caption television

TV broadcasts that provide translated dialogue in the form of subtitles. Also called the “line-21” system because the caption is inserted into blank line 21 of the picture.

Text telephones (TTs)

Telephones that send, receive, and print messages through thousands of stations across the United States.

Mowat sensor

A handheld ultrasound travel aid that uses high-frequency sound to detect objects.

Laser Cane

A mobility device for people who are blind. It converts infrared light into sound as light beams strike objects.

SonicGuide

An electronic mobility device for the blind, which is worn on the head, emits ultrasound, and converts reflections of objects into audible noise.

Personal digital assistants (PDAs

Handheld computer device that can be programmed to perform multiple functions such as making a phone call, reading a newspaper, or maintaining a daily calendar or address book.

Closed-circuit television (CCTV)

A system that includes a small TV camera with a zoom lens, which allows an individual with vision loss to view printed material enlarged up to 60 times its original size.

Atropinization

Treatment for cataracts that involves washing the eye with atropine, permanently dilating the pupil