American Sign Language: Abbreviated ASL. A complete, complex language that employs signs made with the hands and other movements, including facial expressions and postures of the body, used primarily by people in North America who are deaf.
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Autosomal: Pertaining to a chromosome that is not a sex chromosome; relating to any one of the chromosomes save the sex chromosomes.
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Autosomal recessive: A genetic condition that appears only in individuals who have received two copies of an autosomal gene , one copy from each parent. The gene is on an autosome , a nonsex chromosome . The parents are carriers who have only one copy of the gene and do not exhibit the trait because the gene is recessive to its normal counterpart gene.
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Bilateral: Having, or relating to, two sides. Bilateral is as opposed, for example, to unilateral (which means having, or relating to, one side).
Blind: 1. Unable to see. Without part or all of the sense of sight.
2. In a clinical trial, not to know the treatment given or received. The participant is not told whether they are in the experimental or control arm of the study. Also called masked.
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Blindness: Loss of useful sight. Blindness can be temporary or permanent. Damage to any portion of the eye, the optic nerve, or the area of the brain responsible for vision can lead to blindness. There are numerous (actually, innumerable) causes of blindness. The current politically correct terms for blindness include visually handicapped and visually challenged.
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Brain: That part of the central nervous system that is located within the cranium ( skull ). The brain functions as the primary receiver, organizer and distributor of information for the body. It has two (right and left) halves called "hemispheres."
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Cell: The basic structural and functional unit in people and all living things. Each cell is a small container of chemicals and water wrapped in a membrane .
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Central vision: Straight-ahead vision. Central vision is the work of the macula, a small area in the center of the retina that contains a rich collection of cones. (The retina is made up of two types of cells, the cones and the rods. Millions of cones are packed into the macula. The cones are nerve cells sensitive to light, fine detail, and color.) Central vision permits a person to read, drive, and perform other activities that require fine, sharp, straight-ahead vision. As opposed to peripheral vision.
Chromosome: A visible carrier of the genetic information.
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Chromosomes: The microscopically visible carriers of the genetic material. They are composed of deoxyribonucleic acid (DNA) and proteins and, under a microscope, look like little rods.
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Clinical trial: See: Clinical trials. See also: Inconclusive clinical trial; Negative clinical trial; Non-inferior clinical trial; Positive clinical trial.
Clinical trials: Trials to evaluate the effectiveness and safety of medications or medical devices by monitoring their effects on large groups of people.
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Cochlear: Pertaining to the cochlea, the organ of hearing.
Cure: 1. To heal, to make well, to restore to good health. Cures are easy to claim and, all too often, difficult to confirm.
2. A time without recurrence of a disease so that the risk of recurrence is small, as in the 5-year cure rate for malignant melanoma .
3. Particularly in the past, a course of treatment. For example, take a cure at a spa.
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Deafness: Deafness is defined by partial or complete hearing loss. Levels of hearing impairment vary from a mild but important loss of sensitivity to a total loss of hearing. Older adults suffer most often from hearing loss. Age-related hearing loss affects 30 to 35 percent of the population between the ages of 65 and 75 years, and 40 percent of the population over the age of 75. The most common cause of hearing loss in children is otitis media, a disorder that affects predominantly infants and young children. A substantial number of hearing impairments are caused by environmental factors such as noise, drugs, and toxins. Many sensorineural hearing losses result from a genetic predisposition.
Diagnosis: 1 The nature of a disease ; the identification of an illness. 2 A conclusion or decision reached by diagnosis. The diagnosis is rabies . 3 The identification of any problem. The diagnosis was a plugged IV.
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Electronystagmogram: A recording of the eye movements, usually done to confirm the presence of nystagmus. Electronystagmogram may be done in cases of vertigo (dizziness) to determine if there is damage to the vestibular portion of the acoustic nerve. The test may be done in cases of possible acoustic neuroma, Meniere disease, positional vertigo, and labyrinthitis. Abbreviated ENG.
Electroretinogram: Abbreviated ERG. An electroretinographic recording. See: Electroretinography.
ERG: Electroretinography.
Family history: The family structure and relationships within the family, including information about diseases in family members.
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Gene: The basic biological unit of heredity . A segment of deoxyribonucleic acid (DNA) needed to contribute to a function.
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Genes: The basic biological units of heredity . Segments of deoxyribonucleic acid (DNA) needed to contribute to a function.
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Genetic: Having to do with genes and genetic information.
Genetic counseling: An educational counseling process for individuals and families who have a genetic disease or who are at risk for such a disease. Genetic counseling is designed to provide patients and their families with information about their condition and help them make informed decisions.
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Genetic testing: Tests done for clinical genetic purposes. Genetic tests may be done for diverse purposes pertaining to clinical genetics, including the diagnosis of genetic disease in children and adults; the identification of future disease risks; the prediction of drug responses; and the detection of risks of disease to future children.
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Intervention: The act of intervening, interfering or interceding with the intent of modifying the outcome. In medicine, an intervention is usually undertaken to help treat or cure a condition. For example, early intervention may help children with autism to speak. "Acupuncture as a therapeutic intervention is widely practiced in the United States," according to the National Institutes of Health. From the Latin intervenire, to come between.
Involuntary: Done other than in accordance with the conscious will of the individual. The opposite of voluntary.
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Laboratory: A place for doing tests and research procedures and preparing chemicals, etc. Although "laboratory" looks very like the Latin "laboratorium" (a place to labor, a work place), the word "laboratory" came from the Latin "elaborare" (to work out, as a problem, and with great pains), as evidenced by the Old English spelling "elaboratory" designating "a place where learned effort was applied to the solution of scientific problems."
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Mutation: A permanent change, a structural alteration, in the DNA or RNA . In humans and many other organisms, mutations occur in DNA. However, in retroviruses like HIV , mutations occur in RNA which is the genetic material of retroviruses.
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Nerve: A bundle of fibers that uses chemical and electrical signals to transmit sensory and motor information from one body part to another. See: Nervous system.
NIDCD: Stands for National Institute on Deafness and Other Communication Disorders, one of the US National Institutes of Health (the NIH).
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Night blindness: Impaired vision in dim light and in the dark, due to impaired function of specific vision cells (namely, the rods ) in the retina .
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Onset: In medicine, the first appearance of the signs or symptoms of an illness as, for example, the onset of rheumatoid arthritis . There is always an onset to a disease but never to the return to good health. The default setting is good health.
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Optic: Having to do with vision.
Optic nerve: The optic nerve connects the eye to the brain. The optic nerve carries the impulses formed by the retina, the nerve layer that lines the back of the eye and senses light and creates impulses. These impulses are dispatched through the optic nerve to the brain, which interprets them as images. Using an ophthalmoscope, the head of the optic nerve can be easily seen. It can be viewed as the only visible part of the brain (or extension of it).
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Palmitate: An antioxidant and a vitamin A compound that is added to low-fat and fat-free milk to replace the vitamin content lost through the removal of milk fat. Palmitate (more formally known as retinyl palmitate) contains palmitic acid, a 16-carbon saturated fatty acid, which is the major fatty acid found in palm oil. The palmitic acid is attached to the alcohol form of vitamin A, called retinol, to make vitamin A stable in milk. The name "palmitate" comes from the French "palmitique" from palmite, the pith of the palm tree.
Peripheral: Situated away from the center, as opposed to centrally located.
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Peripheral vision: Side vision. The ability to see objects and movement outside of the direct line of vision. Peripheral vision is the work of the rods, nerve cells located largely outside the macula (the center) of the retina. The rods are also responsible for night vision and low-light vision but are insensitive to color. As opposed to central vision.
Pigment: A substance that gives color to tissue. Pigments are responsible for the color of skin, eyes, and hair.
Pregnancy : The state of carrying a developing embryo or fetus within the female body. This condition can be indicated by positive results on an over-the-counter urine test, and confirmed through a blood test, ultrasound, detection of fetal heartbeat, or an X-ray. Pregnancy lasts for about nine months, measured from the date of the woman's last menstrual period (LMP). It is conventionally divided into three trimesters, each roughly three months long.
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Pregnant: The state of carrying a developing fetus within the body.
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Progressive: Increasing in scope or severity. Advancing. Going forward. In medicine, a disease that is progressive is going from bad to worse.
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Puberty: A complex biologic and psychologic process involving sexual development, accelerated growth, and adrenal maturation heralded by the secretion of gonadotropin releasing hormone (GnRH) from a part of the brain called the hypothalamus . This event is the first known step in the reproductive cascade. It initiates the pulsatile release of gonadotropins , gonadal secretion of sex steroids, pubertal development, and gametogenesis (the production of sperm and ova ).
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Recessive: A condition that appears only in individuals who have received two copies of a mutant gene, one copy from each parent. The individuals with a double dose of the mutated gene are called homozygotes. Their parents, each with a single dose of the mutated gene, appear normal and are called heterozygotes, or gene carriers.
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Retina: The retina is the nerve layer that lines the back of the eye, senses light, and creates impulses that travel through the optic nerve to the brain. There is a small area, called the macula, in the retina that contains special light-sensitive cells. The macula allows us to see fine details clearly.
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Retinal: Pertaining to the retina , the extraordinary layer of neurons (nerve cells) that line the back of the eye, which can sense light and create impulses capable of voyaging through the optic nerve to the brain where the impulses are recognized as an image.
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Retinitis pigmentosa: Any one of a large group of inherited disorders in which abnormalities of the photoreceptors (the rods and cones) in the retina lead to progressive visual loss. People with retinitis pigmentosa (RP) first experience defective dark adaptation ("night blindness"), then constriction of the visual field ("tunnel vision") and eventually loss of central vision.
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Sign language: A language that employs signs made with the hands and other movements, including facial expressions and postures of the body, used primarily by people who are deaf. There are many different sign languages as, for example, British and American sign languages. British sign language (BSL) is not easily intelligible to users of American sign language (ASL). Unlike ASL, BSL uses a two-handed alphabet. In developing countries, deaf people may use the sign language of educators and missionaries from elsewhere in the world. For example, some deaf individuals in Madagascar use Norwegian sign language. By contrast, deaf children in Nicaragua have created their own sign language. Study of the emerging Nicaruagan sign language (NSL) has revealed that children naturally possess learning abilities capable of giving language its fundamental structure. See also: American sign language .
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Symptom: Any subjective evidence of disease. Anxiety, lower back pain, and fatigue are all symptoms. They are sensations only the patient can perceive. In contrast, a sign is objective evidence of disease. A bloody nose is a sign. It is evident to the patient, doctor, nurse and other observers.
Syndrome: A set of signs and symptoms that tend to occur together and which reflect the presence of a particular disease or an increased chance of developing a particular disease.
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Trait: In genetics, a trait refers to any genetically determined characteristic. In technical terms, a genetic trait is amenable to segregation analysis rather than quantitative analysis.
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Usher syndrome: A genetic disorder characterized by hearing impairment and an eye disorder called retinitis pigmentosa in which vision worsens over time. Some people with Usher syndrome also have balance problems.
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Vestibular: 1) Having to do with a structure that is a vestibule (entrance), such as the vestibule of the ear. 2) Having to do with the body's system for maintaining equilibrium.
Visual field: The entire area that can be seen when the eye is directed forward, including that which is seen with peripheral vision.
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Visual field test: A test which measures the extent and distribution of the field of vision.
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Vitamin A: Vitamin A is retinol. Carotene compounds (found, for example, in egg yolk, butter and cream) are gradually converted by the body to vitamin A (retinol). A form of vitamin A called retinal is responsible for transmitting light sensation in the retina of the eye.
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Vitamin E: Alpha-tocopherol, an antioxidant vitamin which binds oxygen free radicals that can cause tissue damage. Deficiency of vitamin E can lead to anemia . Vitamin E may play a possible role in preventing heart disease and cancer of the lung and prostate .
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- Visual Field Test - Read about visual field testing and vision tests (Amsler grid, Humphrey-Zeiss and Goldman perimetry tests) for glaucoma and macular degeneration detection.
- Genetic Disease - Learn about genetic disease caused by abnormalities in an individual's genome. There are four types of genetic inheritance, single, multifactoral, chromosome abnormalities, and mitochondrial inheritance. Genetic testing is available for some genetic diseases.
- Electroretinography - Read about electroretinography (ERG), an eye test where electrodes placed on the cornea measure electrical responses to light to try to detect abnormal retinal function.
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