| ophthalmia nivalis | Acute keratoconjunctivitis resulting from exposure to intense ultraviolet irradiation. Synonym: actinic conjunctivitis, arc-flash conjunctivitis, flash keratoconjunctivitis, ophthalmia nivalis, snow conjunctivitis, welder's conjunctivitis. (05 Mar 2000) |
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| ophthalmia nodosa | The presence of nodular swellings on the conjunctiva, due to penetration of ocular tissues by the hairs of caterpillars. Synonym: caterpillar-hair ophthalmia. (05 Mar 2000) |
| ophthalmia, sympathetic | Granulomatous uveitis which follows in one eye after a penetrating injury to the other eye; the secondarily affected eye is called the sympathizing eye, and the injured eye is called the exciting or activating eye. (12 Dec 1998) |
| Egyptian ophthalmia | <ophthalmology> A chronic infectious disease of the conjunctiva and cornea, producing photophobia, pain, lacrimation and blindness. It is one of the oldest infectious diseases known to mankind, and dates back several thousand years with first documentation as early as the pharaonic era in Egypt. The disease is associated with poor socioeconomic conditions in general: with overcrowding, poor personal and environmental hygiene and, in particular, with very limited access to water and sanitation. Trachoma has been eliminated as a blinding disease from several previously hyperendemic countries and regions, both through significant improvements in the socioeconomic status of populations and through specific control efforts. Despite these successes, in many least developed countries of the world blinding trachoma continues to be an important public health problem. In some of the countries where trachoma was once hyperendemic, there remain residual pockets of blinding trachoma and complications, such as inturned eyelashes (trichiasis), which require eyelid surgery. Today, the disease is found mainly in poor rural areas, including parts of central and south America, most African countries and some countries in the Eastern Mediterranean. Trachoma is still endemic in several Asian countries, but there is a lack of updated information from some major populations, e.g. In India and China. The organism that causes this disease is Chlamydia trachomatis; a microorganism resembling both bacteria and viruses, which spreads through contact with eye discharge from the infected person (on towels, handkerchiefs, fingers, etc.) and through transmission by eye-seeking flies. Chlamydia trachomatis provokes an inflammatory reaction in the eye with formation of follicles in the conjunctiva. After years of repeated infections, the inside of the eyelids may be scarred so severely that the eyelid turns inwards with eyelashes rubbing on the eyeball. If untreated, this condition leads to blindness. The World Health Organization is working towards global elimination of trachoma, which is responsible, at present, for at least 15% of the world's blindness. Worldwide, there are about 6 million people largely irreversibly blinded by trachoma, and an estimated 146 million cases of active disease in need of treatment, if blindness is to be prevented. International efforts to eliminate trachoma as a blinding disease will be based on a combination of interventions known by the acronym "SAFE", which stands for Surgery for trichiasis (inturned eyelashes), Antibiotics, Facial cleanliness and Environmental improvement. These interventions will be community-targeted and will seek community involvement through the primary health care approach. Origin: Gr. Trachoma = roughness (07 May 1998) |
| transferred ophthalmia | A serous or plastic uveitis caused by a perforating wound of the uvea followed by a similar severe reaction in the other eye that may lead to bilateral blindness. Synonym: transferred ophthalmia. (05 Mar 2000) |
| endophthalmitis ophthalmia nodosa | Endophthalmitis due to intraocular caterpillar hairs. See: ophthalmia nodosa. (05 Mar 2000) |
| actinic ray | A light ray toward and beyond the violet end of the spectrum that acts upon a photographic plate and produces other chemical effects. Synonym: chemical ray. (05 Mar 2000) |
| alpha ray | <physics> A radioactive particle made up of two protons and two neutrons, these particles are created by the decay of a radioactive material or by nuclear bombardment, and they are the same as the nucleus of a helium-4 atom. (09 Oct 1997) |
| ap, X-ray | An X-ray picture in which the beams pass from front-to-back (anteroposterior). As opposed to a PA (posteroanterior) film in which the rays pass through the body from back-to-front. (12 Dec 1998) |
| beta ray | 1. <radiobiology> Original term used for electrons (and positrons) ejected from decaying nuclei via beta emission. (Label derives from the old days when we had various kinds of radiation emission, and they were labelled alpha, beta, and gamma (the first letters of the Greek Alphabet) because no one really knew what any of them were.) 2. A stream of positive or negative electrons ejected with high energy from a disintegrating atomic nucleus; most biomedically used isotopes emit negative particles (electrons or negatrons, rather than positrons). Cathode rays are low-energy negative electrons produced in cathode ray tubes, also called television tubes or oscilloscopes. (12 Sep 2000) |
| gamma ray | <radiobiology> Electromagnetic radiation (photons) with energies greater than (roughly) 100 keV (that is, 100,000 electron volts). Gamma radiation frequently accompanies alpha and beta decays, and always accompanies fission. Gamma rays are highly penetrating and are best shielded against using dense materials, such as lead or depleted uranium. (Gamma rays are similar to X-rays, but are generally higher in energy and nuclear in origin.) Gamma rays have wavelengths of 1 nanometre or shorter. These are highly energised, deeply penetrating photons which can be emitted from an atomic nucleus during nuclear fission (the splitting of an atom) and during regular atomic decay (radioactivity). (13 Oct 1997) |
| gamma ray knife | A beam of high energy X-rays. See: radiosurgery. (05 Mar 2000) |
| panoramic X-ray | <dentistry> An X-ray taken by a machine that rotates around your head to give the orthodontist a picture of your teeth, jaws and other important information. (08 Jan 1998) |
| panoramic X-ray film | In dentistry, a radiograph taken to give a panoramic view of the entire upper and lower dental arch as well as the temporomandibular joints. (05 Mar 2000) |
| ray | <botany> A zygomorphic flower in the family Asteraceae, a radial band of cells traversing the conducting elements in woody stems. Of a compound umbel, one of the first (lower) series of branches of the inflorescence main stem. (09 Oct 1997) |