A | B | C | D | E | F | G | H | I | K | L | M | N | O | P | R | S | T | U | V | W
A
Abacus
Instrument with sliding counters used for counting or performing calculations.
Abstract Concept
Relates to concepts which can be defined or described, but which are often left up to the perception of the individual (e.g., feelings such as love, nervousness, or excitement).
Accommodation
Ability of the eye to focus at different distances.
Achromatopsia
Congenital defect in which the receptor cells on the retina, called cones, are either absent or defective, resulting in the inability to see colors.
Acoustic Reflexes
Contraction of middle ear muscles because of loud sounds that stimulate the ear; measured with tympanometry.
Acuity Loss
Vision problem that prevents an individual from seeing clearly such as cataracts, dystrophy, nystagmus, and retinitis pigmentosa.
Adventitiously Deafblind
Vision and hearing are present at birth but are lost to some degree later in life.
Advocacy
Taking an active role in the education and care of an individual or the act or process of supporting a cause or person.
Aicardi Syndrome
Rare congenital disorder which occurs only in females. Characteristic features include absence of the corpus callosum (the structure linking the two cerebral hemisphere of the brain), frequent seizures, and abnormalities of the eyes.
Air Conduction
Passing of sound to the inner ear through the outer ear and the middle ear.
Albinism
Partial or total absence of pigment in the skin, hair, and eyes; frequently accompanied by strabismus, nystagmus, reduced acuity, light sensitivity, and poor depth perception.
Alport Syndrome
Characterized by hereditary kidney disorders, deafness, and ocular anomalies (e.g., cataracts). Males are more severely affected than females.
Alstrom Syndrome
Rare inherited disorder characterized by diabetes mellitus, obesity, and a progressive loss of vision and hearing which begins in early childhood. Other symptoms may include progressive kidney disease.
Amblyopia (Lazy Eye)
Reduction in or dimness of vision; no detectable organic cause.
Amplify
Increase the loudness of a sound.
Anencephaly
Birth defect in which all but the most primitive parts of the brain, skull, and spinal cord fail to form in the embryo.
Aniridia
Congenital absence of all or part of the iris.
Anophthalmia
Congenital absence of one or both eyes.
Anoxia/ Asphyxia
Lack of oxygen at birth.
Anterior Chamber
Located behind the cornea; filled with aqueous humor.
Apert Syndrome
Rare genetic disorder which is apparent at birth. The syndrome is characterized by skeletal and associated skull malformations of the head, face, hands, and feet.
Aphakia
Absence of the crystalline lens of the eye, which may be congenital or surgically caused. Causes a loss of accommodation and hyperopia.
Apnea
Pause in breathing that lasts 20 seconds or longer.
Aqueous Humor
Clear liquid that fills the anterior chamber and supplies oxygen and nutrients to the inner part of the eye.
Arousal
Levels of activity from alertness to drowsiness.
Assistive Listening Device (ALD)
Composed of a microphone, transmitter component, receiver, and an earmold; amplifies only the sound source picked up by the microphone.
Astigmatism
Abnormal condition of the eye in which the spherical curve of the cornea is irregular, causing blurred vision; may be corrected with contact lenses or eyeglasses.
Atresia
Absence or closure of a natural passage of the body (e.g., ear canal).
Atrophy
Decrease in size or wasting away of tissue.
Audiogram
Graph used to record the hearing responses of an individual at different frequencies and intensities.
Audiologist
Professional trained in the science of audiology who may assess hearing, determine auditory capacity for processing sound, etc. An individual with a masters or doctorate degree who specializes in hearing assessment and habilitation and rehabilitation of people with hearing disorders.
Audiology
The study of hearing, which involves identification, evaluation, habilitation, and rehabilitation of hearing loss.
Audiometry
Any kind of testing that involves hearing.
Audition
The power or sense of hearing.
Auditory Brainstem Response (ABR)
Hearing test that measures electrical activity at the brainstem in response to sounds; reveals basic information about whether sounds are getting to the brainstem and if the ear is working properly.
Auditory Canal
Structure that leads from the outer ear (auricle/ pinna) to the eardrum (tympanic membrane).
Auditory Cortex
Area where neural impulses are processed into meaningful bits of auditory information.
Auditory Nerve
Eighth cranial nerve that carries auditory impulses/ messages from the inner ear to the brainstem and brain. This nerve is the 8th cranial nerve which carries auditory messages from the inner ear to the brainstem and brain. Problems may include auditory nerve tumors, damage, or problems in development.
Auditory Processing Problem
Hearing loss that results from damage to the auditory nerve, brainstem, or auditory cortex.
Aural
Pertaining to the ear or hearing.
Auricle
(see Outer Ear)
B
Bardet-Biedl Syndrome
Inherited rare disorder. Characteristics of this syndrome include mental retardation, degeneration of the retinas of the eyes, kidney abnormalities, delayed sexual development or underdeveloped reproductive organs, obesity, and/or abnormal fingers and toes.
Basilar Membrane
Membrane extending the length of the cochlea in the inner ear that contains hair cells or nerve cells for hearing. Different sections of the basilar membrane respond better to different sound frequencies, which are perceived by the brain as pitches.
Batten Disease
Progressive degenerative disease which is fatal. The child develops normally until 6-18 months of age and then begins to lose motor and cognitive skills. Seizures, mental retardation, and severe visual impairment occur.
Behavioral Observation Audiometry (BOA)
Hearing test. A professional presents sounds to an individual and watches for the individual’s responses to the sounds.
Bilateral Hearing Loss
Hearing loss in both ears.
Binocular Vision
Ability to use both eyes simultaneously to focus on the same object, fusing the two images into one.
Blind Spot
Blank area in the visual field corresponding to the position of the optic nerve, or an area of absent or reduced sensitivity anywhere in the visual field.
Blindness
Inability to see; absence or severe reduction of vision.
Body Aid
Type of hearing aid that has a receiver inside a small box worn on the body.
Bone Conduction
Passing of sound to the inner ear through vibration applied to the bones in the skull, instead of through the outer and middle ear.
Braille
Raised dots that represent letters and numbers; used by blind individuals.
Brailler
Machine that creates braille.
Brain Injury
Injury to the brain caused by a brain bleed in prematurely, trauma, infections, or other events that affect functioning in various ways.
Brainstem
Portion of the brain between the cerebrum and the spinal cord that controls the functions of breathing, swallowing, seeing, and hearing.
Brainstem Evoked Response (BSER)
See Auditory Brainstem Response.
C
Captioning
Process of providing printed subtitles for auditory information.
Cataract
Condition in which the lens of the eye appears cloudy or opaque.
Central Auditory Processing Disorder
Hearing may be inconsistent and vary from day to day, because the ability of the brain to process sound is affected.
Central Field Loss
Eye condition in which affected individuals cans see well from the sides but have poor or no central vision; the opposite of tunnel vision.
Cerebral Palsy
Disorder of movement and posture due to a nonprogressive defect of the immature brain.
Cerumen
Ear wax. The glands that make cerumen are located in the ear canal.
CHARGE
Very rare hereditary disorder that must include at least four of the following six characteristics: C – coloboma (defect or lesion of the eye), H – heart defect/disease, A – atresia of the choanae, R – retarded growth and development, G – genital abnormalities, E – ear abnormalities and/or deafness.
Choroid
Located behind the retina; filled with blood vessels that provide oxygen and nutrients to keep the retina alive.
Choroideremia
Condition in which vision is impacted first with the onset of night blindness, then field restrictions, and then acuity and color vision, resulting in blindness in later years; occurs more in males.
Ciliary Bodies
Muscles attached to the iris that pull on the eye lens to change its shape and help to focus the vision. Also produces aqueous humor, the clear fluid that fills the front of the eye.
Closed Circuit Television (CCTV)
High tech vision device; electronically enlarges print material on a television screen.
Cochlea
Snail-shaped structure in the inner ear containing the organ of hearing.
Cochlear Implant
Prosthetic for hearing that must be surgically implanted.
Cockayne Syndrome
Rare inherited disorder characterized by growth retardation, mental retardation, retinal atrophy, abnormal sensitivity to light, and progressive sensorineural hearing loss of later onset
Cogan Syndrome
Rare eye disorder that occurs most frequently in young and middle-aged females. It usually affects only one eye and develops slowly over time. It is associated with tinnitus, vertigo, and usually deafness.
Cognitive Development
Development of mental processes; can be adversely affected by sensory loss.
Cognitive Skills
Thinking, reasoning, and other intellectual abilities.
Coloboma
Notch or cleft in the pupil, iris, lens, retina, choroid, or optic nerve. Its location determines the degree of vision loss. There may be decreased acuity, photophobia, field loss, refractive errors, and poor depth perception.
Color Deficiency
(Color blindness) Inability, partial or complete, to discriminate among colors.
Computer Assisted Real Time Translation (CART)
Produces a caption; used in live situations where a written script is not available for captioning in advance.
Concept
Something conceived in the mind, a thought or notion; an abstract or generic idea generalized from particular experiences; a mental representation, image or idea of tangible and concrete objects (e.g., a chair, a dog) and intangible ideas and feelings (e.g., colors, emotions).
Concept Development
Developing concepts. A concept is something conceived in the mind (e.g., thought or notion), an abstract or generic idea, or a mental representation, image, or idea of concrete objects as well as of intangible ideas.
Concrete Concept
Relates to objects or things that are tangible (e.g., a car, a chair).
Conductive Hearing Loss
Hearing loss that results from a blockage or malfunction of the outer or middle ear (e.g., otitis media or ear infection).
Cone
Part of the photoreceptors that gives information about color. There are red, green, and blue cones, which each respond to different frequencies of the light spectrum. The retina contains approximately six million cones.
Congenital
Originating from birth.
Congenital Rubella Syndrome
Also known as the German or three day measles. This is caused by the exposure of a fetus to the rubella virus. The areas affected in the fetus include vision, hearing, and heart. The most common vision problems include cataracts, glaucoma, microphthalmia, hypoplasia of the iris, macular lesions, optic atrophy, colobomas, nystagmus, and strabismus. Visual acuity and visual fields are reduced.
Congenital Syphilis
Chronic infectious disease acquired by the fetus in the uterus. Early symptoms include low birth weight, fever, and skin problems. Sensorineural hearing loss of slow progressive nature occurs.
Congenitally Deaf/Adventitiously Blind
Having a hearing impairment or being deaf from birth or early childhood and experiencing vision loss in adult life; the most common cause is Usher’s Syndrome, the combination of congenital deafness and Retinitis Pigmentosa.
Congenitally Deafblind
Having both visual and hearing impairment since birth or early childhood; a common cause is Congenital Rubella Syndrome as a result of maternal Rubella during pregnancy.
Conjunctiva
Mucous membrane that lines the eyelids and covers the front part of the eyeball.
Conjunctivitis
Pink eye or inflammation of the conjunctiva; caused by bacteria, viruses, or allergies.
Cornea
The transparent dome-shaped window covering the eye where light enters the eyeball.
Cornelia de Lange Syndrome
Rare genetic disorder that is characterized by short stature, microcephaly, small hands and feet, distinctive facial appearance including long eyelashes, eyebrows that grow together, upturned nostrils, thin upper lip, low-set ears, and low hairline. The range and severity of symptoms varies across individuals.
Cortex
Outer layers of the cerebrum and cerebellum of the brain that contains most of the higher nervous centers such as those concerned with hearing and vision.
Cortical
Relating to the cortex.
Cortical Visual Impairment (CVI)
The brain is unable to process the visual information sent to it from the eyes through the visual pathways.
Cri-Du-Chat Syndrome
enetic disorder caused by the loss or partial deletion of the short arm chromosome 5. The more severe the deletion, the lower the height, weight, and intelligence. Vision concerns often include strabismus, myopia, glaucoma, microphthalmus, colobomas, and optic atrophy.
Crigler-Najjar Syndrome
Rare inherited disorder characterized by the absence of an enzyme in the liver. High levels of billirubin result, causing damage to the central nervous system.
Crouzon Syndrome
Rare genetic disorder characterized by malformations of the skull and face, bulging of the eyeballs, widely spaced eyes, underdeveloped upper jaw, and protrusion of the lower jaw.
Cued Speech
Educational tool designed for parents of deaf children that corresponds exactly to the spoken language of the parent. There are eight different handshapes, each representing a group of consonant sounds, four positions around the mouth, each of which represent different vowel sounds and non-manual information found on the mouth.
Cytomegalovirus (CMV)
Herpes type of virus which occurs continuously in the population. Manifestations of this disease may be minimal (e.g., rash and fever) or severe (e.g., microcephaly, mental retardation, and profound sensorineural hearing loss).
D
Dandy Walker Syndrome
Rare malformation of the brain that is present at birth. It is characterized by an abnormally enlarged space at the back of the brain which interferes with the normal flow of cerebrospinal fluid. As a result, excessive amounts of fluid accumulate around the brain and cause pressure within the skull, swelling of the head, and neurological impairment.
Deafblind/DeafBlind/Deaf-Blind
Term applied to those who have a degree of both vision loss and hearing loss.
Decibel (dB)
Measurement used for intensity (loudness) of sounds.
Degree (of the hearing loss)
Hearing losses are categorized according to the degree of the loss, for example, mild, moderate, severe, and profound.
Delayed Visual Maturation (DVM)
Absence of visual responsiveness despite normal and intact visual pathways. In time, it is followed by a gradual improvement of visual functioning when the child is two to three years old.
Depth Perception
Ability to judge depth or the relative distance of objects in space and to orient one’s position in relation to them.
Diabetes Insipidus
Condition in which blurred vision and a central scotoma (blind spot) appear in one eye. It is treated with the hormone vasopressin.
Diabetic Retinopathy
Disorder in which repeated hemorrhage results in permanent opacity of the vitreous humor; blindness may eventually result; occurs most frequently in individuals with long-standing, poorly controlled diabetes.
Diopter
Unit of measurement used to indicate how much light rays are refracted or bent by a lens.
Diplopia
Seeing one object as if it were two.
Directive or passive environment
An environment where most things are done for the child or to the child with deafblindness with few opportunities for choice making, problem-solving, communication or interaction.
Discrimination of Sounds
Ability to tell the difference between sounds and to respond appropriately.
Dome Magnifier
Low tech vision device.
Down Syndrome
Syndrome characterized by hypotonia, flat facial profile, upwardly slanted eyes, small low-set ears, short stature, mental retardation, small nose with a low nasal bridge, and spots at the periphery of the iris. Individuals with Down Syndrome have an extra chromosome and may have congenital heart problems and hearing loss.
E
Ear Canal
“Tunnel” that connects the pinna and the eardrum.
Eardrum (Tympanic Membrane)
Layer of tissue shaped like a cone at the end of the ear canal; moves back and forth and causes the bones in the middle ear to move; separates the middle ear from the outer ear.
Earmold
Plastic fitting that fits into the canal or ear flap of the ear to conduct sound directly into an individual’s hearing system from a hearing aid. Earmolds are also intended to remove the possibility of feedback or squealing.
Encephalitis
Inflammation of infection of the brain, usually viral in nature.
Environment
All of the objects, circumstances, and events surrounding an individual.
Epithelium
Layer of cells that form the epidermis of the skin and the surface layer of mucous membranes.
Esotropia
Abnormal turning inward of one eye.
Etiology
Cause or origin.
Eustachian Tube
Small tube running from the middle ear into the throat; provides fresh air to the middle ear and allows fluid to drain from the middle ear.
Exotropia
Abnormal turning outward of one eye.
Extraocular Muscles
Six muscles which control eye movement: superior oblique, superior rectus, lateral rectus, inferior oblique, inferior rectus, and medial rectus.
F
Familial Exudative Vitreo Retinopathy (FEVR)
Hereditary disorder that affects vision in both eyes, mildly (acuity loss, strabismus, nystagmus) or severely (total retinal detachment).
Fetal Alcohol Syndrome (FAS)
This syndrome is distinguished by congenital birth defects (e.g., growth deficiency, facial malformations, central nervous system problems, major organ system defects). Vision deficits include strabismus, myopia, astigmatism, optic nerve hypoplasia, nystagmus, and glaucoma in adulthood.
Field Loss
Reduction in the area visible to the eyes when they are fixating straight ahead.
Fine Motor Skills
Use of the hands to explore and manipulate objects in the environment.
Fixation Ability
Ability of the eyes to direct gaze on an object and hold it steadily in view.
Flashing/Vibrating Alarm
Alarms that can be hooked to telephones, doorbells, and fire alarms.
FM System
Frequency modulated device; type of listening device.
Focus
Point to which rays of light are brought to a sharp image point after passing through a lens.
Fovea
Small depression on the retina of the eye; the part of the macula adapted for the clearest vision.
Frequency
Pitch of a sound; number of cycles produced in one second; measured in Hertz (Hz).
Functional Vision
Presence of enough usable vision that the individual has the ability to use sight as a primary channel for learning or living. Relates to the total act of seeing and how the individual uses sight to function.
Functional Vision Assessment
Testing how an individual uses vision.
G
Genetic
Traits passed on from one generation to another.
Glaucoma
Disease of the eye caused by increased intraocular pressure, resulting either from a malformation or a malfunction of the eye’s drainage structrues.
Goldenhar Syndrom
Rare disorder that is apparent at birth. There is a wise spectrum of symptoms and physical features across individuals. These include anomalies of the eyes, ears, mouth, cheekbones, jaw, and vertebrae.
Gustatory
Associated with eating or the sense of taste.
H
Hallgren Syndrome
Characterized by an eye disorder and congenital sensorineural hearing loss. Retinitis pigmentosa, progressive ataxia, and mental retardation occur in 25 percent of individuals.
Hand-under-hand
A technique used to guide an individual’s hands in which the guide lightly places his/her hands under the individual’s hands.
Head Trauma
njury to the head, especially to the scalp and cranium. The injury may be limited to soft tissue damage or may include the cranial bones and the brain.
Hearing
Detection of sound.
Hearing Aid
Device with a sound receiver and an earmold that fits into the ear; amplifies speech and environmental sounds.
Hearing Aid Dealer
Salesperson who specializes in the sale of hearing aids and assistive listening devices.
Hearing Threshold
Intensity at which a person can just barely hear a particular sound.
Hemianopsia
Field loss that occurs when a specific portion of the optic pathway malfunctions, usually because of pressure from a tumor. The degree of the field loss depends on the type, amount, and location of the pressure. Field losses can be corresponding (the same in both eyes) or opposite. They may involve half fields or quadrants, or affect upper or lower fields.
Hertz (Hz)
Measurement used for the frequency (pitch) of sounds.
Hunter Syndrome
Rare metabolic disorder characterized by a deficiency of an enzyme which breaks down nutrients. As a result, there is an abnormal accumulation of complex carbohydrates in cells within various bodily tissues which causes physical symptoms and abnormalities.
Hurler Syndrome
Rare genetic disorder caused by the deficiency of an enzyme, resulting in the inability to break down complex carbohydrates. It is a form of MPS.
Hydrocephalus
Condition in which dilated cerebral ventricles inhibit the normal flow of cerebrospinal fluid (CSF). The CSF accumulates in the skull and puts pressure on the brain tissue, which includes the optic nerve and visual cortex. Visual functioning varies. Eye conditions include strabismus, nystagmus, refractive errors, optic nerve atrophy, and DVM.
Hyperopia
Farsightedness; condition of the eye in which light rays from distance objects are brought to focus behind the retina when the eye is at rest, making it difficult to see up close.
Hypersensitivity
Oversensitivity to stimuli.
Hypertonic
Stiff, increased tone, resistance to passive movement.
Hypoplasia
Condition of arrested development in which an organ or other body part remains below the normal size or in an immature state.
I
IEP
Individual education plan for children who have special needs in the educational environment.
IFSP
Individual family service plan for children who are receiving early intervention services.
Impedance Audiometry/ Immittance Testing
Test that determines the presence of middle ear fluid, middle ear pressure, mobility of the eardrum and the middle ear bones, and Eustachian tube function.
Incidental Learning
Learning that occurs unintentionally or by chance; often done through vision and hearing.
Incus (anvil)
One of the three small bones in the middle ear; shaped like an anvil, attached to the malleus and the stapes; helps to amplify the sound coming from the outer ear.
Infection
Condition in which the body or a part of the body is invaded by a pathogenic agent which produces injurious effects.
Inferior Oblique
One of four muscles that controls the vertical motion of the eyeball. Rotates the eye so that the top of the eye moves away from the nose.
Inferior Rectus
One of four muscles that controls the vertical motion of the eyeball. Moves the eye down.
Inner Ear
Includes the semicircular canals, the cochlea, and the auditory nerve. Problems in this part of the ear may include damaged or missing nerve cells and damage to the balance mechanism.
Intensity
Volume or loudness; measured in decibels (dB).
Interpreter
Individual who is trained to provide access to information for an individual who is Deaf.
Interpreter Tutor
Paraprofessionals who often work one-on-one with students; usually only work in schools.
Intervener
A person who works consistently one-to-one with an individual who is deafblind, and who has training and specialized skills related to deafblindness.
Intervention
A process that creates access to visual and auditory information and connects the child to the world.
Iris
Ring-shaped muscle that controls the size of the pupil and the amount of light that enters the eye.
K
Kearns-Sayre Syndrome
Rare neuromuscular disorder characterized by heart disease, progressive paralysis of certain eye muscles, abnormal accumulation of colored material on the membrane lining of the eyes which leads to inflammation, degeneration, and wearing away of certain eye structures.
Keratoconus
Rare degenerative disease, occurring in the second decade of life, in which the cornea becomes cone-shaped, thins in the center, and may rupture.
Kinesthetic
A sense mediated by end organs located in muscles, tendons, and joints and stimulated by bodily movements and tensions. A sensory experience derived from this sense.
Klippel-Feil Sequence
Rare condition that is apparent at birth. It is characterized by a short and wide neck, low hairline and the back of the neck, reduction in the number of cervical vertebrae, and fusion of the cervical spine.
Klippel-Trenaunay-Weber Syndrome
are disorder that is present at birth. It is characterized by abnormal benign growths on the skin, excessive growth of the soft tissue and bone of the limbs, and varicose veins. Individuals may also have purplish-reddish birthmarks. Symptoms vary across individuals.
Kniest Dysplasia
Type of dwarfism characterized by short arms and legs, a round face, swelling and stiffness of the joints, and contractures of the fingers.
L
Lateral Rectus
One of two muscles that controls the horizontal motion of the eyeball. Moves the eye away from the nose.
Laurence-Moon-Biedl Sydrome
Hereditary condition consisting of retinitus pigmentosa, mental retardation, hypogonadism, obesity, and polydactyly. The individual first experiences a decrease in night vision, then peripheral vision diminishes, and a loss of central vision follows. Depth perception is poor. Other eye symptoms include cataracts, strabismus, myopia, photophobia, and small eyes.
Leber Congenital Amaurosis
Rare genetic eye disorder. Onset occurs at birth or within the first few years of life. Symptoms may include strabismus, nystagmus, unusual sensitivity to light, clouding of the lenses of the eye, protrusion of the front of the eye, hearing loss, mental retardation, and delay of mental and muscular activity.
Leber’s Optic Atrophy
Rare hereditary condition, largely affecting males, in which vision loss of rapid onset occurs. It starts in one eye, moves to the other eye, and often leads to total blindness.
Legally Blind
20/200 or worse in the better eye with the best possible correction.
Leigh Disease
Rare inherited neurometabolic disorder that occurs between the ages of 3 months and 2 years. It is characterized by the degeneration of the brain, spinal cord, and optic nerve. Symptoms include progressive neurological deterioration and loss of previously acquired skills.
Lens
Clear, flexible disk that helps the eye focus light onto the retina.
Light Perception
Ability to distinguish the absence or presence of light.
Little Room
Small environment that contains consistently placed objects, which helps an infant who is deafblind to reach out and explore.
Low Vision Aids
Optical and non-optical devices of various types, such as magnifiers, lenses, hand-held telescopes, and reading stands, which are useful to people with visual impairments.
Low Vision Specialist
Professional trained to help individuals enhance and utilize their residual vision using various optical devices.
M
Macula
Small area of the retina of the eye that surrounds the fovea and that, with the fovea, is responsible for the detailed central vision.
Macular Area
Section of the retina where cones are very dense. (These cones discriminate fine details straight ahead.)
Macular Degeneration
Hereditary condition in which the cones in the central part of the retina degenerate.
Malleus (mallet)
One of the three small bones in the middle ear; shaped like a hammer, attached to the eardrum and the incus; starts a rocking motion along the ossicles.
Marfan Syndrome
Inherited disorder of the connective tissue, bones, muscles, ligaments, and skeletal structures. It is characterized by a tall lean body type with long extremities, abnormal joint flexibility, dislocation of the lens of the eye, cataracts, secondary glaucoma, myopia, strabismus, corneal flatness, and nystagmus.
Maroteaus-Lamy Syndrome
Rare genetic disorder caused by the deficiency of enzymes resulting in the inability to metabolize complex carbohydrates. As a result, growth retardation, joint stiffness, abnormalities in the bones of the hands and spine, and coarsening of the facial features occur.
Marshall Syndrome
Rare genetic disorder which is characterized by a flattened nasal bridge, nostrils that tilt upward, widely-spaced eyes, myopia, cataracts, and hearing loss.
Medial Rectus
One of two muscles that controls the horizontal motion of the eyeball. Moves the eye towards the nose.
Memory Box
Box or container that holds objects, etc. that are related to an individual’s past experiences; the objects help the individual remember and talk about those experiences.
Menginitis
Inflammation of the lining surrounding the brain and the spinal chord, which is caused by different organisms such as bacteria or viruses. The central nervous system may be affected, and some loss of sight or changes in vision may occur (e.g., strabismus, decreased acuity, cortical visual impairment, and photophobia due to changes in the sizes of the pupils.)
Meniere’s Syndrome
Disorder of the inner ear that is marked by recurrent attacks of dizziness, tinnitus, and deafness (Merriam-Webster’s Collegiate Dictionary).
Meningitis
Inflammation of the lining surrounding the brain and spinal cord, which may result in loss of sight or changes in vision.
Microcephaly
Characterized by an exceptionally small head (head circumference is more than two standard deviations below the average size).
Microphthalmia
Hereditary, congenital birth defect in which one or both eyes are much smaller than normal.
Microscope
Low tech vision device that enlarges objects.
Middle Ear
Includes the ear drum, three tiny middle ear bones (malleus, incus, and stapes), and the Eustachian tube. Problems in this part of the ear may include infection, hole in the eardrum, broken middle ear bones, or bony growth.
Mild Hearing Loss
Hearing loss of 25 to 40 dB. Makes it difficult to understand soft-spoken speech and to pay attention, especially in noisy environments.
Mixed Hearing Loss
Results from having a conductive hearing loss and a sensorineural hearing loss at the same time.
Mobility
Denotes the ability to navigate from one’s present fixed position to one’s desired position in another part of the environment.
Moderate Hearing Loss
Hearing loss of 41 to 55 dB. An individual with a 40 dB loss would need to be 3-5 feet from the sound source to hear it.
Moderately Severe Hearing Loss
Hearing loss of 56 to 70 dB. Sounds must be very loud for an individual with a 70 dB loss to hear.
Moebius Syndrome
Rare developmental disorder that is characterized by facial paralysis at birth. There are abnormalities of the facial muscles and jaw as a result of absent or diminished facial nerve development. There may also be abnormalities of the mouth and face and malformations of the limbs.
Monocular
Pertaining to one eye. Also is used to mean a hand-held telescope (low tech device).
Morquio Syndrome
Rare genetic disorder caused by the deficiency of enzymes, resulting in the inability of the body to metabolize complex carbohydrates. As a result, bony abnormalities of the head, chest, hands, knees, and spine may occur.
Motivation
Desire to accomplish a goal or participate in an endeavor.
Motor Planning
Ability to automatically start, perform, and complete a series of movements to achieve a desired outcome.
Mowat Sensors
Devices that are attached to travel canes to translate objects in space into specific vibration patterns.
Muscle Balance
Ability of the six extraocular eye muscles of each eye to pull together to allow binocular vision to occur in all directions.
Mutual Tactile Attention
Touching along with an individual who is deafblind in a way that lets him/her know the tactile experience is a shared one.
Myopia
Defect in vision resulting in the inability to see objects distinctly at a distance.
N
Nearsighted
Able to see up-close better than far away.
Neonatal Herpes Simplex
Rare disorder which is transferred by a parent with oral or genital herpes to offspring before, during, or shortly after birth. The disorder can range from mild to severe.
Neural Impulses
Light that has been transformed into electric signals that travels along the optic nerve to the brain.
Neural Tube Defects
Congenital defect caused by failure of the neural tube to close during embryonic growth such as spinal bifida, cleft lip, and cleft palate.
NF1 – Neurofibromatosis
Inherited disease characterized by benign tumors that may occur anywhere in the body, including the eyelids and orbital portion of the optic nerve. Brown spots and developmental anomalies (especially in the bones, muscles, and abdominal organs) occur. Curvature of the spine can develop.
NF2 – Bilateral Acoustic Neurofibromatosis
Rare genetic disorder that is characterized by benign tumors of the acoustic nerve. Symptoms may include unsteady gait, dizziness, headache, facial numbness, tinnitus, and increasing deafness.
Night Blindness
An individual with this condition may be able to see with no problems by day or in good illumination (light), but is unable to see at night or in faint light. Can be caused by any eye condition that affects the rods of the eye.
Nonprogressive Vision Problem
Vision problem that remains the same over time (e.g., does not improve or worsen).
Norrie Disease
Rare form of sex-linked hereditary blindness which occurs in newborn males. It is characterized by retinal detachment and may be associated with mental retardation, diabetes, short stature, and/or progressive hearing loss.
Nystagmus
Involuntary rapid movements of the eyes.
O
Object Schedule
Book, binder, etc. that contains representative objects that help an individual know what activity he/she will be participating in next.
Octave
Interval between two frequencies, one of which is twice as large as the other (for example 250 Hz and 500 Hz).
Ocular
Pertaining to the eye.
Ocularist
Professional who specializes in the making and fitting of artificial eyes.
Oculomotor Apraxia
Rare inherited neurological disorder present at birth which is characterized by impairment in horizontal eye movements and difficulty converging (to move toward one point) and diverging (to move outward from a common point) on an object.
Oculomotor Problems
Individuals with these problems have trouble moving their eyes, so it is difficult for them to look at and follow the movement of objects and people.
Olfactory
Related to, or connected with, the sense of smell.
Ophthalmologist
Doctor who routinely examines eyes for infections, injury, and malformations; also tests for visual acuity and problems with visual field, color, and contrast sensitivity.
Optic Disc
The area from where all of the neural fibers leave the eyeball.
Optic Nerve
Nerve that transmits neural impulses from the retina to the brain.
Optic Nerve Atrophy
Inability of the optic nerve to conduct electrical impulses to the brain, resulting in loss of vision, which ranges from minimal to total. It is caused by pressure on the optic nerve from glaucoma, tumors, hydrocephalus, trauma, etc.
Optic Nerve Hypoplasia
Failure of the optic nerve(s) to develop normally, such that the nerve(s) are not fully functioning.
Optician
Professional who grinds lenses, fits them into frames, and dispenses and adjusts glasses or other optical devices on the written prescription of an optometrist or physician.
Optico-Cochleo-Dentate Degeneration
Eye and nervous system disorder which is characterized by progressive visual and sensorineural hearing loss as well as progressive spastic quadriplegia.
Optometrist
Licensed, nonmedical eye practitioner who treats vision problems nonmedically through use of glasses, prisms, and eye exercises. In some states, he/she may also diagnose and treat some eye conditions with medications.
Orientation
Process through which an individual who is visually impaired uses his/her remaining senses to establish his/her position and relationship to all other significant objects in the environment.
Orientation and Mobility
Orientation is knowing where you are and being able to plan how to go where you want to go. Mobility is the actual movement from place to place.
Orientation and Mobility Specialist
Professional who has specialized training to teach children with visual impairments; teaches about space, directions, travel techniques, and adaptive devices.
Orthopist
Provides vision training to help the eyes work together in order to produce binocular vision.
Ossicle Chain
Three small connected bones in the middle ear.
Otitis Media
Fluid or an infection in the middle ear which is alleviated by antibiotics or tubes inserted in the ear to drain the fluid.
Otoacoustic Emissions (OAE)
A hearing test which measures acoustic emissions (sounds) that are generated in the cochlea and reflected back through the middle ear to the external ear. This tests the functioning of the cochlea.
Otolaryngologist
Physician who is knowledgeable in diseases of the ear, nose, and throat (ENT).
Otologist
Physician who specializes in the anatomy, physiology, and pathology of the ear.
Outer Ear
Also known as the auricle or pinna; includes the ear flap and the ear canal; Gathers and enhances sound and channels it to the middle ear. Problems in this part of the ear may include wax buildup in the canal, a foreign object in the ear canal or outer ear, and/or the ear canal not forming correctly or missing.
Oval Window
pening between the middle and the inner ear.
Oxotoxic Drugs
Drugs that can damage the cochlea of an unborn child.
P
Passive or directive environment
An environment where most things are done for the child or to the child with deafblindness with few opportunities for choice making, problem-solving, communication or interaction.
Peripheral Vision
Outer part of the visual field; side vision.
Persistent Hyperplastic Primary Vitreous (PHPV)
Condition that usually affects one eye, which is slightly small and has a cataract. Surgery is often needed to salvage vision, and visual prognosis ranges from mild to severe.
Pfieffer Syndrome
Rare disorder characterized by abnormalities of the head and face, malformations of the fingers and toes, and/or additional physical abnormalities.
Photons
Little bits of energy that make up light.
Photophobia
Abnormal sensitivity to or discomfort from light.
Photoreceptors
Specialized cells called rods and cones that make up the retina; triggered by light that enters the eyes.
Pierre-Robin Syndrome
Craniofacial-skeletal disorder characterized by cleft soft palate, large jaw area, external ear malformations, and dental anomalies. Eye conditions include glaucoma, neurofibromatosis, retinoblastoma, and colobomas.
Pinna
Visible part of the ear—the outer folds and the ear lobe; gathers sound waves in and enhances them as they move into the ear canal.
Pitch
Highness or lowness of sound.
Play Audiometry
Sounds are presented to an individual who is taught to respond by doing a fun activity.
Posterior Chamber
Interior area in the eye behind the lens.
Prader-Willi
Genetic disorder characterized by failure to grow and gain weight during infancy, feeding problems, short stature, low muscle tone, and genital abnormalities. Obesity may develop between the ages of 6 months and 6 years. Individuals have characteristic facial features including almond-shaped eyes, a thin upper lip, and full cheeks. Additional abnormalities may include strabismus, small hands and feet, curvature of the spine, and mild to severe mental retardation.
Profound Hearing Loss
A hearing loss of 90 dB or higher. Individuals with this loss cannot use auditory receptive communication.
Progressive Vision Problem
Vision problem that gradually worsens over time.
Proprioceptive
Awareness of body movement, positions, and directions.
Ptosis
Drooping of the upper eyelid (one or both) slightly or entirely over the pupil.
Pupil
The hole in the middle of the iris that appears black.
Pure Tone
Simple sound wave used in testing hearing.
Pure Tone Audiometry
Hearing test. Tones at specific test frequencies are presented through earphones. The individual’s response to these sounds is recorded on an audiogram.
R
Reactive or responsive environment
An environment that provides opportunities for the child to make choices, solve problems, communicate, and develop a sense of self.
Reading Stand
Device that supports regular or large print books and allows the reader to change the position.
Reduced (or absent) Color Sensitivity
Vision problem that causes color confusion and night blindness.
Reduced Contrast Sensitivity
Vision problem that limits the eye’s ability to distinguish between the lightness and darkness of objects.
Refraction
1. Deviation or bending of rays of light when passing from one clear substance to another of a different density. 2. The determination of refractive errors in the eye and their correction with lenses.
Refractive Error
Condition that occurs when light rays entering the eye are not bent enough or are bent too much, so that they are not brought to a sharp focus on the retina. This results in myopia (nearsightedness), hyperopia (farsightedness), or astigmatism.
Refsum Syndrome
Rare hereditary disorder of lipid metabolism in which phytanic acid cannot be broken down. Symptoms may include retinitis pigmentosa, degenerative nerve disease, ataxia, and abnormalities of the bones and skin.
Residual Hearing
Any measurable hearing that a hearing-impaired individual retains.
Residual Vision
Vision available to an individual who is not totally blind.
Responsive or reactive environment
An environment that provides opportunities for the child to make choices, solve problems, communicate, and develop a sense of self.
Retina
Thin sensory tissue which lines the back of the eye. It contains millions of photoreceptors (rods and cones) that capture light and convert them into electrical impulses. These impulses travel along the optic nerve to the brain where they are turned into images.
Retinal Detachment
Separation of the inner layer of the retina from the outer layer, resulting in loss of retinal function.
Retinitis CMV (Cytomegalovirus)
Virus that leads to a variety of effects on the fetus. Vision problems include blurred vision, photophobia, distorted images, and central blind spots.
Retinitis Pigmentosa
A rare hereditary disease which is characterized by retinal degeneration and progressive blindness. It begins with night blindness in adolescence or in adult life.
Retinoblastoma
Rare, slow growing tumor that is located on the retina of the eye.
Retinopathy of Prematurity (ROP)
Destructive retinal changes that sometimes develop after prolonged life-sustaining oxygen therapy is given to a premature infant. These changes can result in a minimal loss of vision to a total loss of vision in one or both eyes.
Rod
Part of the photoreceptors that are primarily responsible for peripheral and night vision and provide information about movement and shapes. There are approximately 125 million rods in the human eye.
Rubella
Infectious disease known as German measles. When pregnant women in the first trimester contract rubella, it affects the fetus in the areas of vision, hearing, and heart.
S
Saccadic Movements
Quick movements of both eyes together in the same direction for scanning objects and fixation.
Sclera
Tough outside layer of the eyeball, which is sometimes called the “white of the eye”; made up of crisscrossing fibers. Serves as the eye’s protective outer coat.
Scotoma
Field loss that consists of isolated blind spots.
Semicircular Canals
Three fluid-filled canals in the ear that help maintain balance.
Semi-Concrete Concept
Relates to an action, color, position, or something that can be demonstrated but not held in one’s hand (e.g., jumping, behind, red).
Sensorimotor
Related to functioning in both sensory and movement aspects of bodily activity.
Sensorineural Hearing Loss
Occurs as a result of damage in or a defect of the inner ear (cochlea or auditory nerve).
Sensory Integration
Organization of sensory information to enable the child to act on and interact with the environment.
Sensory Stimulation
Rousing or invigoration of the senses – vision, audition, tactile, olfactory, gustatory, or kinesthetic.
Septo Optic Dysplasia or De Morsier’s Syndrome
Syndrome characterized by growth hormone deficiencies and visual deficits, which range from normal visual acuity to subtle visual field changes, to no light perception.
Severe Hearing Loss
Hearing loss of 71 to 90 dB. An individual with this loss may understand loud speech at a distance of 1 foot in a quiet environment.
Shaken Baby Syndrome
Syndrome that results from shaking an infant.
Signal to Noise Ratio
Difference in volume between the main sound source and the surrounding sounds.
Signed Language
Alternative communication form.
Skill
The execution of learned physical tasks; a learned power of doing something competently, a developed aptitude or ability.
Smell
A sense that can give information from a distance.
Smith-Limli-Opitz Syndrome
Hereditary developmental disorder characterized by nostrils that tilt forward, drooping eyelids, webbing between the second and third toes, small stature, male genital abnormalities, and mental retardation.
Sound
Produced by vibrations that cause air molecules to move back and forth.
Sound Wave
Pressure wave set in motion by any event that generates energy. This pressure wave is detected by the hearing mechanism as sound.
Speech Perception
The ability to be aware of speech.
Speechreading
Alternative communication form.
Stapes (stirrup)
Small bone, shaped like a stirrup, attached to the incus and the oval window; amplifies sound waves coming from the outer ear.
Stickler Syndrome
Genetic disorder characterized by congenital abnormalities of the eye, small jaw, and cleft palate. Bone abnormalities and degenerative changes in some joints may occur early in life.
Strabismus
Eye disorder in which the eye turns inward or outward. Caused by one or more improperly functioning eye muscles.
Stroke
Abnormal condition of the blood vessels of the brain characterized by a blockage from an embolus or cerebrovascular hemorrhage. Depending upon where the brain is affected and the extent of the decreased blood supply to the brain, paralysis, weakness, a speech defect, aphasia, or death may occur.
Sturge-Weber Syndrome
Congenital disease characterized by three major symptoms including excessive blood vessel growth, intracranial calcification, and seizures. Facial birth marks usually appear on one side of the face.
Superior Oblique
One of four muscles that controls the vertical motion of the eyeball. Rotates the eye so that the top of the eye moves towards the nose.
Superior Rectus
One of four muscles that controls the vertical motion of the eyeball. Moves the eye up.
T
Tactile
Pertaining to the sense of touch.
Tactile Sensitivity
Condition of being sensitive to touch; common among children who are deafblind.
Tactile Sign Language
Communication method based on a standard manual sign system in which the receiver’s hand(s) is placed lightly upon the hand(s) of the signer to perceive the signs.
Taste
A sense. Distinguishes the sweet, sour, bitter, or salty quality of a dissolved substance.
Tay-Sachs Disease
Progressive nervous system disorder characterized by deafness, blindness, and seizures. The disease is fatal, usually by the age of four.
Threshold
Softest level of intensity at which a person hears a particular sound.
Tinnitus
Noises heard from within the head (e.g., ringing, pulsating, or buzzing).
TORCH Syndrome
Syndrome characterized by a variety of eye conditions, which, in turn, may result in such things as acuity and field loss. TORCH is an acronym for Toxoplasmosis, Other agents, Rubella, Cytomegalovirus, and Herpes simplex.
Touch
Special sense by which pressure or traction exerted on the skin is perceived (Merriam-Webster’s Collegiate Dictionary). Probably the most important sense to an individual with deafblindness; may include use of feet, arms, legs, hands, back, stomach, etc.
Toxoplasmosis
Infectious disease caused by a parasitic organism and can be acquired or present at birth. Lesions of the central nervous system occur, which lead to blindness brain defects, and other serious conditions.
Treacher-Collins Syndrome
Rare inherited disorder characterized by abnormalities of the head and face, including flattened area around the cheekbones, small mandible, malformation of the external ears, dental abnormalities, and cleft palate. Affected individuals have a conductive hearing loss.
Trisomy 13
Rare chromosomal disorder in which the range and severity of associated symptoms vary across individuals. These symptoms may include small wide-set eyes, cleft lip and palate, extra fingers and toes, scalp defects, malformed low-set ears, microcephaly, mental retardation, kidney malformations, and congenital heart defects.
Trisomy 18
Rare chromosomal disorder in which symptoms vary across individuals. These symptoms may include malformations of the head and face, small jaw, malformed low-set ears, widely spaced eyes, drooping of upper eyelids, malformations of the hands and feet including overlapped flexed fingers, congenital heart defects, undescended testes, growth deficiency, feeding and breathing difficulties, and mental retardation.
Tuberous Sclerosis
Rare genetic neurological disorder characterized by seizures, mental retardation, and skin/ eye lesions. There my be tumors in the eyes, and visual functioning can vary depending on the size and severity of the tumors. There may be decreased visual acuity, retinal scarring, retinal detachment, myopic, field loss, or glaucoma.
Tumor
Growth of tissue characterized by progressive, uncontrolled proliferation of cells. It may be localized or invasive, benign or malignant.
Tunnel Vision
Eye condition in which the field of vision is 20 degrees or less.
Turner Syndrome
Rare chromosomal disorder which affects females. It is characterized by short stature, lack of sexual development, broad chest with widely spaced nipples, webbed neck, congenital hear defects, and kidney abnormalities.
Tympanic Membrane
See eardrum.
Tympanometry
Testing of the middle ear with equipment that bounces sound off the tympanic membrane under different pressure conditions.
U
Unilateral Hearing Loss
A hearing loss occurring in one ear.
Usher Syndrome
Inherited recessive genetic disorder characterized by sensorineural hearing impairment, present at birth or shortly thereafter, and a progressive loss of field due to retinitis pigmentosa.
V
Vestibular Nerve
Carries information about balance.
Vestibular System
Semicircular canals and vestibular nerve.
Video Relay
Video telecommunication service that allows deaf, hard-of-hearing individuals to communicate over video telephones and similar technologies with hearing people in real-time, via a sign language interpreter.
Viral Infection
Infection caused by a virus; examples include meningitis and encephalitis.
Vision
Ability of the brain to process information received from the eye.
Vision Stimulation
Series of activities and exercises designed to increase an individual’s visual capabilities.
Visual Acuity
Ability of the eyes to distinguish object details and shape. Common visual activity measurement is 20/20.
Visual Cortex
Part of the brain that processes visual information.
Visual Discrimination
Ability to match or determine exact characteristics of two forms when one of the forms is among similar forms.
Visual Field
Space visible to the eyes when they are fixating straight ahead.
Visual Processing Problem
Vision problem often caused by brain damage. The eyes collect and transmit information correctly, but the brain does not process it precisely.
Visual Tracking
Ability to follow the movement of an object with the eyes.
Visually Reinforced Audiometry (VRA)
Sounds are presented to an individual, and the individual looks to find the source of the sound. Also called Conditioned Orientation Reflex (COR).
Vitreous Humor
Clear, jelly-like substance that fills the posterior chamber and keeps the eye shaped like a ball.
Vogt-Koyanagi-Harada Syndrome
Rare disease that affects the eyes, ears, skin, and covering of the brain and spinal cord. The main symptom is rapid loss of vision. There may be sever headaches,vertigo, nausea, drowsiness, loss of hearing, loss of hair and skin color, and whitening of the hair and eyelashes.
W
Waardenburg Syndrome
Congenital genetic disorder which varies across individuals. Characteristics may include facial abnormalities, irises of different colors, diminished coloration of the hair and skin, white forelock, wide nasal bridge, and a sensorineural hearing loss.
Wildervanch Syndrome
Rare genetic disorder that primarily affects females. It is characterized by retraction of the eyeball, abnormalities of the eye movements, and congenital sensorineural hearing loss. Physical abnormalities may also be present.
Wolf-Hirschhorn Syndrome
Rare chromosomal disorder characterized by wide-set eyes, broad or beaked nose, microcephaly, low-set malformed ears, heart defects, seizures, and mental and growth deficiencies.