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Electroretinography
Electroretinography Abbreviated ERG. A test in which the electrical potentials generated by the retina of the eye are measured when the retina is stimulated by light. In an ERG, an electrode is placed on the cornea at the front of the eye. The electrode measures the electrical response of the rods and cones, the visual cells in the retina at the back of the eye. An ERG may be useful in the evaluation of hereditary and acquired disorders of the retina. A normal ERG shows the appropriate responses with increased light intensity. An abnormal ERG is found in conditions such as arteriosclerosis of the retina, detachment of the retina, and temporal arteritis with eye involvement. The instrument used to do electroretinography is an electroretinograph and the resultant recording is called an electroretinogram.
RELATED TERMS--------------------------------------
ERG
Electroretinography.
Retina
A membrane lining the inside of the back of the eye that contains light-sensitive nerve cells that convert focused light into nerve impulses, making vision possible.
Cornea
The front part of the eye that acts as a window for the entrance of light rays. It is attached to the other outer coat of the eye, the sclera; the white part of the eye. The cornea provides a significant amount of focusing power for the eye (the rest is provided by the lens). Because it has many nerve fibers, an injury or foreign body causes significant pain and discomfort.
Eye
The organ of sight. The eye has a number of components. These components include but are not limited to the cornea, iris, pupil, lens, retina, macula, optic nerve, choroid and vitreous.
Rods
The rods are the visual cells of the retina that are important for night vision and peripheral vision. The rods are the first affected in rod-cone degenerations such as RP.
Hereditary
Transmitted from parent to offspring; derived from ancestry.
Acquired
"Anything that is not present at birth but develops some time later. In medicine, the word ""acquired"" implies ""new"" or ""added."" An acquired condition is ""new"" in the sense that it is not genetic (inherited) and ""added"" in the sense that was not present at birth. For example, AIDS (the acquired immune deficiency syndrome) is an acquired form of immune deficiency due to the acquisition of HIV (the human immunodeficiency virus). An acquired mutation is a change in a gene that occurs in a single cell after the conception of the individual. That change is then passed along to all cells descended from that cell. Acquired mutations are involved in the development of cancer."
Abnormal
Not normal. Deviating from the usual structure, position, condition, or behavior. In referring to a growth, abnormal may mean that it is cancerous or premalignant (likely to become cancer).
Arteriosclerosis
Commonly called "hardening of the arteries;" a variety of conditions caused by fatty or calcium deposits in the artery walls causing them to thicken.
Detachment
A behavior pattern characterized by general aloofness in interpersonal contact; may include intellectualization, denial, and superficiality.
Temporal
Having to do with the side of the head.
Arteritis
Inflammation of blood vessels (arteries). Causes problems in the organs or tissues supplied by those arteries.
Electroretinography
Abbreviated ERG. A test in which the electrical potentials generated by the retina of the eye are measured when the retina is stimulated by light. In an ERG, an electrode is placed on the cornea at the front of the eye. The electrode measures the electrical response of the rods and cones, the visual cells in the retina at the back of the eye. An ERG may be useful in the evaluation of hereditary and acquired disorders of the retina. A normal ERG shows the appropriate responses with increased light intensity. An abnormal ERG is found in conditions such as arteriosclerosis of the retina, detachment of the retina, and temporal arteritis with eye involvement. The instrument used to do electroretinography is an electroretinograph and the resultant recording is called an electroretinogram.
Electroretinogram
ERG. A test that measures the functional integrity of the retina, including the rod and cone photoreceptors. Usually involves the use of dilating drops in the eye and use of a contact lens electrode.
SIMILAR TERMS--------------------------------------
Elective
In medicine, something chosen (elected). An elective procedure is one that is chosen (elected) by the patient or physician that is advantageous to the patient but is not urgent.
Elective mutism
Failure to speak, or to be able to speak about certain topics, that is not necessarily permanent but is reversible under changed circumstances.
Elective surgery
Surgery that is subject to choice (election). The choice may be made by the patient or doctor. For example, the time when a surgical procedure is performed may be elective. The procedure is beneficial to the patient but does not need be done at a particular time. As opposed to urgent or emergency surgery.
Electro-oculography
EOG. A type of electrophysiologic retinal testing done to measure the difference in the electrical potential between the front and back of the eye in response to dark and light.
Electrocardiogram
ECG or EKG. A test that records the electrical activity of the heart, shows abnormal rhythms (arrhythmias or dysrhythmias), and detects heart muscle damage.
Electrocardiogram (EKG or ECG)
A test that records on graph paper the electrical activity of the heart via small electrode patches attached to the skin. An EKG helps a physician determine the causes of abnormal heartbeat or detect heart damage.
Electrocoagulation
A procedure that uses an electrical current passed through an endoscope to stop bleeding in the digestive tract and to remove affected tissue.
Electrocochleography
A test that measures the electrical potentials generated in the inner ear in response to stimulation by sound. Electrocochleography may be done, for example, to confirm the diagnosis of Ménière disease. Abbreviated ECochG (or ECoG).
Electroconvulsive
A type of therapy used to treat severe, unresponsive depression by passing electrical current through the brain.
Electroconvulsive therapy
A procedure in which an electric current is passed through the brain to produce controlled convulsions (seizures) to treat patients with depression, particularly for those who cannot take or are not responding to antidepressants, have severe depression, or are at high risk for suicide. Electroconvulsive therapy (ECT) is believed to act by a massive neurochemical release in the brain due to the controlled seizure. The most common side effect is short-term memory loss, which usually resolves quickly. ECT typically relieves depression within 1 to 2 weeks after beginning treatments.
Electrocutophilia
A paraphilia of the sacrificial and expiatory stratagem in which sexuoerotic arousal and orgasm is dependent upon the use of electrical stimulation of the body to possibly include the nipples, urethra, penis/scrotum, vulva/clitoris/vagina and anal/rectal tissues. This paraphilia has been seen to occur more frequently among women than in men and has also resulted in accidental death. The activities of electrocutophilia may be exploratory or varietal sex play and not a paraphilia. It also may be part of a sadomasochistic repertory. Devices for "safe" sexuoerotic electrostimulation are now commercially available.
Electrodesiccation
Use of an electric current to destroy cancerous tissue and control bleeding.
Electroencephalogram
A study of electrical current within the brain. Electrodes are attached to the scalp. Wires attach these electrodes to a machine which records the electrical impulses. The results are either printed out or displayed on a computer screen. Electroencephalogram is abbreviated EEG. Different patterns of electrical impulses can denote various problems within the brain including different forms of epilepsy. Most EEGs see only a moment in time within the brain, and can catch only gross abnormalities in function. An overnight EEG is designed to check the electrical activity in the brain of a sleep-deprived patient, increasing the chance that seizure activity will be revealed. Also available are 24- or 48-hour EEGs, which measure electrical activity over one or two days, usually using mobile EEG units.
Electrogastrogram
An electrogastrogram is a study in which the electrical current generated by the muscle of the stomach is sensed and recorded. Thus, it is analogous to an electrocardiogram of the heart. The electrogastrogram, like the electrocardiogram, is performed by taping electrodes to the skin; however, in the case of the electrogastrogram the electrodes are placed on the upper abdomen over the stomach. The recordings from the muscle are stored and analyzed by a computer. The electrogastrogram is performed to diagnose motility disorders of the stomach, that is, when the muscles of the stomach are not working normally.
Electrolarynx
A battery-operated instrument that makes a humming sound to help people who have lost their larynx to talk.
Electrolysis
For cosmetic reasons, a method of removing hair by inserting a needle into the hair-growing follicle and killing it with a pulse of electric current.
Electrolyte
One of the substances in the blood that helps to regulate the proper balance of body fluids. Examples of electrolytes include sodium and potassium.
Electrolytes
Chemicals such as salts and minerals needed for various functions in the body.
Electromyogram
EMG. A test to evaluate nerve and muscle function.
Electromyography (EMG) and Nerve Conduction Velocity (NCV) Studies
Tests used to diagnose neuropathy and check for nerve damage. These tests are usually both run at the same time, using the same equipment.
Electron beam computerized tomography (EBCT)
A new noninvasive test for the detection of coronary artery disease (CAD). EBCT, or Ultrafast CT (as the technique will be termed here) is designed to measure calcium deposits in the coronary arteries.
Electron microscope
Abbreviated EM. A microscope in which an electron beam replaces light to form the image. EM has its pluses (greater magnification and resolution than optical microscopes) and minuses (you are not really "seeing" objects, but rather you are looking at their electron densities, and meaningless artifacts may abound). Nonetheless, EM has extended the range of the microscope.
Electron microscopy
Abbreviated EM. Microscopy in which an electron beam replaces light to form the image. EM has its pluses (greater magnification and resolution than optical microscopes) and minuses (you are not really "seeing" objects, but rather you are looking at their electron densities, and meaningless artifacts may abound). Nonetheless, EM has extended the range of the microscope.
Electronic fetal monitor
A device that monitors a fetus's progress and vital signs when a woman is in labor. Records the fetal heartbeat and the mother's contractions.
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.
Electronystagmography
A neurologic test which measures fine motor movements of the eye muscles, used to confirm the presence of nystagmus.
Electrooculogram
EOG. A test of the functional integrity of the Retinal Pigment Epithelium (RPE) – a layer of cells next to the retina of the eye. The EOG involves electrodes attached to the inner and outer corners of the eye and the patient is required to look back-and-forth between two small lights in a large white globe (ganzfeld) with bright lights on and off.
Electrophoresis
A process by which molecules (such as proteins, DNA, or RNA fragments) can be separated according to size and electrical charge by applying an electric current to them. Each kind of molecule travels through the medium at a different rate, depending on its electrical charge and molecular size.
Electrophoretic
Pertaining to electrophoresis, the separation of molecules according to their size and electrical charge by applying an electric current to them.
Electrophysiologic
Pertaining to electrophysiology.
Electrophysiologic retinal testing
Testing done to diagnose specific disorders of the retina, including inherited retinal diseases, the effects of toxic drug exposure on the retina, and the presence of foreign bodies within the eye.
Electrophysiologic study of the heart
A test of the electrical conduction system of the heart (the system that generates the heart beat).
Electrophysiological
Pertaining to electrical results produced through physiological agencies, or by change of action in a living organism.
Electrophysiological study (EPS)
A cardiac catheterization to study electrical current in patients who have arrhythmias.
Electrophysiology
That branch of physiology which treats of electric phenomena produced through physiological agencies.
Electrophysiology (EP) Study
An EP Study is a recording of the electrical activity your heart. This test is used to help your doctor find out the cause of your rhythm disturbance and the best treatment for you. During the test, your doctor may safely reproduce your arrhythmia, then give you medications to see which one controls it best.
Electroretinogram
ERG. A test that measures the functional integrity of the retina, including the rod and cone photoreceptors. Usually involves the use of dilating drops in the eye and use of a contact lens electrode.
Electrosurgery
Instead of using a scalpel, the surgeon utilizes a heat-generating electrical device to burn or vaporize tissue in order to remove it and minimize and halt bleeding.
PREVIOUS AND NEXT TERMS--------------------------------------
Electrophoresis
A process by which molecules (such as proteins, DNA, or RNA fragments) can be separated according to size and electrical charge by applying an electric current to them. Each kind of molecule travels through the medium at a different rate, depending on its electrical charge and molecular size.
Electrophoretic
Pertaining to electrophoresis, the separation of molecules according to their size and electrical charge by applying an electric current to them.
Electrophysiologic
Pertaining to electrophysiology.
Electrophysiologic retinal testing
Testing done to diagnose specific disorders of the retina, including inherited retinal diseases, the effects of toxic drug exposure on the retina, and the presence of foreign bodies within the eye.
Electrophysiologic study of the heart
A test of the electrical conduction system of the heart (the system that generates the heart beat).
Electroretinography
Electrosurgery
Instead of using a scalpel, the surgeon utilizes a heat-generating electrical device to burn or vaporize tissue in order to remove it and minimize and halt bleeding.
Elevated hemidiaphragm
Elevation of half of the diaphragm, the muscle that separates the chest cavity from the abdomen and that serves as the main muscle of respiration. The elevation of a hemidiaphragm is a significant sign of a problem.
Eleventh cranial nerve
The eleventh cranial nerve is the accessory nerve. The twelve cranial nerves, the accessory nerve included, emerge from or enter the skull (the cranium) as opposed to the spinal nerves which emerge from the vertebral column. The accessory is so-called because, although it arises in the brain, it receives an additional (accessory) root from the upper part of the spinal cord.
Elliptocytosis
Hematologic disorder characterized by elliptically shaped red blood cells (elliptocytosis) with variable breakup of red cells (hemolysis) and varying degrees of anemia. Inherited as a dominant trait. Due to mutation (change) in one of the genes encoding proteins of the red cell membrane skeleton.
EM (electron microscope)
A microscope in which an electron beam replaces light to form the image. EM stands for electron microscope (the device) and for electron microscopy (the technique and field).
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