radiation cataract

cataract /cat·a·ract/ (-rakt) an opacity of the crystalline lens of the eye or its capsule.catarac´tous

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after-cataract  a recurrent capsular cataract.

atopic cataract  cataract in those with long-standing atopic dermatitis.

black cataract  see senile nuclear sclerotic c.

blue cataract , blue dot cataract blue punctate opacities scattered throughout the nucleus and cortex of the lens.

brown cataract , brunescent cataract see senile nuclear sclerotic c.

capsular cataract  one consisting of an opacity in the lens capsule.

complicated cataract  secondary c.

congenital cataract 

1. cataract present at birth, usually bilaterally; it may be mild or severe and may or may not impair vision depending on size, density, and location.

2. developmental c.

coronary cataract  tiny white opacities in a ring around the lens, the center and periphery of the lens remaining clear.

cortical cataract 

1. developmental punctate opacity common in the cortex and present in most lenses. The cataract is white or cerulean, increases in number with age, but rarely affects vision.

2. the most common senile cataract; white, wedgelike opacities are like spokes around the periphery of the cortex.

cupuliform cataract  a senile cataract in the posterior cortex of the lens just under the capsule.

developmental cataract  a type of small cataract in youth, resulting from heredity, malnutrition, toxicity, or inflammation, seldom affecting vision.

electric cataract  one occurring after an electric shock, especially to the head. Anterior subcapsular cataracts may form and develop within days; slowly developing or stationary opacities may follow a shock not to the head.

glassblowers' cataract , heat cataract posterior subcapsular opacities caused by chronic exposure to infrared (heat) radiation.

hypermature cataract  one with a swollen, milky cortex, the result of autolysis of the lens fibers of a mature cataract.

lamellar cataract  one affecting only certain layers between the cortex and nucleus of the lens.

mature cataract  one producing swelling and opacity of the entire lens.

membranous cataract  a condition in which the lens substance has shrunk, leaving remnants of the capsule and fibrous tissue formation.

morgagnian cataract  a mature cataract in which the cortex has liquefied and the nucleus moves freely within the lens.

nuclear cataract  one in which the opacity is in the central nucleus of the eye.

overripe cataract  hypermature c.

polar cataract  one at the center of the anterior (anterior polar c.) or posterior (posterior polar c.) pole of the lens.

pyramidal cataract  a conoid anterior cataract with its apex projecting forward into the aqueous humor.

radiation cataract  one caused by ionizing radiation, e.g., x-rays, or by nonionizing radiation, e.g., infrared (heat) rays, ultraviolet rays, microwaves.

ripe cataract  mature c.

secondary cataract  one resulting from disease, e.g., iridocyclitis; degeneration, e.g., chronic glaucoma, retinal detachment; or from surgery, e.g., glaucoma filtering, retinal reattachment.

senile cataract  cataract in the elderly.

senile nuclear sclerotic cataract  slowly increasing hardening of the nucleus, usually bilateral and brown or black, with the lens becoming inelastic and unable to accommodate.

snowflake cataract , snowstorm cataract one marked by gray or blue to white flaky opacities, seen in young diabetics.

total cataract  an opacity of all the fibers of a lens.

toxic cataract  that due to exposure to a toxic drug, e.g., naphthalene.

traumatic cataract  one due to injury to the eye.

zonular cataract  lamellar c.

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radiation cataract,

Etymology: L, radiare, to emit rays; Gk, katarrhaktes, portcullis

a cataract that is caused by excessive exposure of the eye to x-rays or other types of radiation that cause a change in the protein molecules of the lens.

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radiation (rā´dēā´shn),

n 1. the process of emitting radiant energy in the form of waves or particles.
n 2. the combined processes of emission, transmission, and absorption of radiant energy.

radiation, actinic,

n radiation capable of producing chemical change (e.g., effect of light and roentgen rays on photographic emulsions).

radiation, background,

n radiation arising from radioactive material other than the one directly under consideration. Background radiation resulting from cosmic rays and natural radioactivity is always present. Background radiation may also exist because of radioactive substances in other parts of a building (e.g., building material).

Radiation.

radiation, backscatter,

n radiation that deflects off its target at an angle of deflection greater than 90°, possibly affecting those who may be off to the side of or behind the main beam. See also radiation, scattered.

radiation, biologic effectiveness of,

n the ability of a particular type of ionizing radiation to produce biologic effects on an organism with small absorbed doses. See relative biologic effectiveness.

radiation, bremsstrahlung

n (white), describes the distribution of roentgen rays from extremely low energy photons to roentgen rays originating from the highest kilovoltage applied to a radiographic tube.
Bremsstrahlung translates to “braking radiation,” referring to the sudden slowing of electrons that occurs when they encounter nuclei with a high positive charge.

radiation caries,

n a type of tooth decay caused by the reduction in saliva that may result from the use of ionizing radiation in the treatment of oral and facial malignancies. Radiation caries is an unfortunate side effect of a necessary radical procedure to cure or prevent the spread of cancer.

radiation cataract,

n a cataract that is caused by extended exposure of the eye to ionizing radiation in the course of treating facial cancers.

radiation, characteristic,

n radiation that originates from an atom after removal of an electron or excitation of the nucleus. The wavelength of the emitted radiation is specific, depending only on the element concerned and on the particular energy levels involved. Also refers to the specific type of secondary radiation resulting when rays from a radio ray tube strike another substance, such as copper.

radiation, coherent scattering,

n See coherent scattering.

radiation, Compton scatter,

n See Compton scatter radiation.

radiation, corpuscular

n subatomic particles, such as electrons, protons, neutrons, or alpha particles, that travel in streams at various velocities. All the particles have definite masses and travel at various speeds. The properties are in opposition to electromagnetic radiations, which have no mass and travel in wave forms at the speed of light. See also radiation, electromagnetic.

radiation, cosmic,

n See ray, cosmic.

radiation, cumulative effect of

n reactions vary depending on the dosage; if the radiation received is in several smaller doses, the reaction is not as severe as if the same amount of radiation is received all at once. Unless a tissue is completely destroyed by the radiation, some or all of it will be repaired, although cumulative damage may cause some irreparable conditions.

radiation, dermatitis,

n See dermatitis, radiation.

radiation detector,

n a device for converting radiant energy to a form more suitable for observation and recording. Examples include radiograph films and radiometers.

radiation, direct,

n (primary radiation), radiation emanating from a tube aperture and comprising the useful beam, as compared with any stray radiation, such as that which comes from the tube container.

radiation, electromagnetic,

n forms of energy propagated by wave motion, such as photons or discrete quanta. The radiations have no matter associated with them, as opposed to corpuscular radiations, which have definite masses. They differ widely in wavelength, frequency, and photon energy and have strikingly different properties. Covering an enormous range of wavelengths (from 10⁻⁶ to 10¹⁷ Å), they include radio waves, infrared waves, visible light, ultraviolet radiation, gamma rays, and cosmic radiation. See also radiation, corpuscular.

radiation exposure,

n a measure of the ionization produced in air by roentgen rays or gamma rays. It is the sum of the electric charges on all ions of one sign that are produced when all electrons liberated by photons in a volume of air are completely stopped, divided by the mass of air in the volume element. The unit of exposure is the roentgen.

radiation field,

n See radiographic beam, field size.

radiation, gamma,

n See ray, gamma.

radiation, genetic effects of,

n See genetic effects of radiation.

radiation, grenz,

n See ray, grenz.

radiation, hard,

radiation consisting of the short wavelengths (higher kilovolt peak equals greater penetration).

radiation hazard,

n See hazard, radiation.

radiation, heterogeneous

n a beam or “bundle” of radiation containing photons of many wavelengths.

radiation, homogeneous,

n a beam of radiation consisting of photons that all have the same wavelength.

radiation hygiene,

n See hygiene, radiation.

radiation intensity,

n See intensity, radiation.

radiation, ionizing,

n electomagnetic radiation such as roentgen rays and gamma rays; particulate radiation such as alpha particles, beta particles, protons, and neutrons; all other types of radiations that produce ionization directly or indirectly.

radiation leakage,

n (stray radiation), the escape of radiation through the protective shielding of the radiography unit tube head. This radiation is detected at the sides, top, bottom, or back of the tube head; it does not include the useful beam.

radiation, monochromatic,

n See radiation, homogeneous.

radiation necrosis,

n See necrosis, radiation.

radiation, neutron,

n See ray, neutron.

radiation oncology,

n the study of the treatment of cancer using ionizing radiation

radiation osteomyelitis/osteonecrosis

n an infection of the bone that occurs after exposure to radiation. Most commonly seen in cancer patients when radiation therapy damages healthy tissue surrounding the targeted tumor.

radiation, primary,

n all radiation produced directly from the target in a radiographic tube. See also radiation, direct.

radiation protection,

n provision designed to reduce exposure to radiation. For external radiation, this provision consists of using protective barriers of radiation-absorbing material, ensuring adequate distances from the radiation sources, reducing exposure time, and combinations of these measures. For internal radiation, it involves measures to restrict inhalation, ingestion, or other modes of entry of radioactive material into the body.

radiation quality,

n the ability of a beam of radiographs to allow the production of diagnostically useful radiographs. Usually measured in half-value layers of aluminum and controlled by the kilovolt peak.

radiation quantity,

n amount of radiation. The amount of exposure is expressed in roentgens (R), whereas quantity of dose is expressed in rads.

radiation, relative biologic effectiveness of (RBE),

n a comparison between various types of ionizing radiation with respect to the ability to produce biologic effects with small doses.

radiation, remnant,

n the radiation passing through an object or part being examined that is available either for recording on a radiographic film or for measurement.

radiation, scattered,

n (backscatter radiation), radiation whose direction has been altered. It may include secondary and stray radiation.

radiation, secondary,

n the new radiation created by primary radiation acting on or passing through matter.

radiation shield,

n See shield, radiation.

radiation sickness,

n a self-limited syndrome characterized by varying degrees of nausea, vomiting, diarrhea, and psychic depression after exposure to very large doses of ionizing radiation, particularly doses to the abdominal region. Its mechanism is not completely understood. It usually occurs a few hours after treatment and may subside within a day. It may be sufficiently severe to necessitate interrupting the treatment series, or it may incapacitate the patient.

radiation, soft,

n radiation consisting of the long wavelengths (lower kilovolt peak results in less penetration).

radiation, speed of,

n the speed of light, or approximately 186,000 miles per second.

radiation, stray,

n See radiation leakage.

radiation survey,

n See survey, radiation.

radiation therapy,

n See therapy, radiation.

radiation, total body,

n the exposure of the entire body to penetrating radiation. In theory, all cells in the body receive the same overall dose.

radiation treatment,

n a cancer treatment method that uses roentgen rays to modify or destroy cancer cells; dental patients who are undergoing radiation therapy may exhibit an increased need for certain nutrients. See also therapy, radiation.

radiation, useful,

n the part of the primary radiation that is permitted to pass from the tube housing through the tube head port, aperture, or collimating device. See beam, useful.

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cataract

opacity of the lens of the eye or its capsule or both. Cataract may result from injuries to the eye, exposure to great heat or radiation, or inherited factors. Rare in cattle and swine, common in dogs. Treatment consists of surgical removal of the lens (lens extraction or cataract extraction). May affect the entire lens or be localized, e.g. posterior polar cataract.

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acquired cataract

any non-congenital cataract; usually the result of trauma, systemic disease or another eye disorder.

after-cataract

1. any membrane of the pupillary area after extraction or absorption of the lens.

2. secondary cataract (below).

capsular cataract

one consisting of an opacity of the capsule of the lens.

complicated cataract

a cataract occurring secondarily to other intraocular disease.

congenital cataract

present at birth; often not progressive. See also white eye calf syndrome.

cortical cataract

an opacity in the cortex of the lens. The common form of cataract in dogs; inherited in many breeds, often in association with progressive retinal atrophy.

developmental cataract

one that occurs at any age before the animal becomes an adult.

diabetic cataract

one associated with diabetes mellitus.

electric cataract

one caused by electrical current as in electrocution.

embryonal cataract

one caused by prenatal influences.

focal ring cataract

a perinuclear opacity with normal lens fibers surrounding it. Usually the result of an in utero or neonatal insult to the lens.

galactosemic cataract

see galactosemia.

hyaloid cataract

a focal opacity at the point where the hyaloid artery meets the posterior lens capsule. See also mittendorf's dot.

hypermature cataract

one in which the lens has begun to liquefy.

immature cataract

incomplete opacity.

incipient cataract

a very early stage of development with no impairment of vision.

inherited cataract

occurs in a number of breeds of cattle, often in combination with other abnormalities of the eye. Affected calves are usually normal in other respects and can be reared if the inconvenience of their blindness can be overcome. Also occurs in dogs, often with late onset and in association with other inherited ocular defects such as progressive retinal atrophy.

intumescent cataract

a mature cataract that has become swollen.

juvenile cataract

one developing in very young animals, for example dogs less than 6 months of age.

lenticular cataract

opacity of the lens not affecting the capsule.

mature cataract

one in which the lens is completely opaque.

morgagnian cataract

liquefaction, except the nucleus which drops to the bottom of the lens, and shrinkage of the capsule.

nuclear cataract

one involving the nucleus of the lens; the common form of congenital cataracts.

nuclear Y cataract

a form of congenital cataract in which small opacities outline the Y suture of the nucleus.

nutritional cataract

see galactosemia.

radiation cataract

one caused by radiation, as in radiotherapy.

reduplication cataract

a capsular opacity covered by another layer of epithelium.

secondary cataract

1. one that forms after most of the lens has been removed.

2. complicated cataract.

senile cataract

occurs in the aged of all species, preceded by nuclear sclerosis.

subcapsular cataract

may be anterior or posterior. Inherited in several breeds of dogs.

toxic cataract

one caused by exposure to a toxic substance.

traumatic cataract

one caused by trauma.