conjunctivitis [key], inflammation or infection of the mucosal membrane that covers the eyeball and lines the eyelid, usually acute, caused by a virus or, less often, by a bacillus, an allergic reaction, or an irritating chemical. Commonly called pinkeye, mild conjunctivitis usually causes redness, discharge, and itching of the membrane. Conjunctivitis may also be associated with upper respiratory infection or with childhood diseases such as measles. Bacterial forms of the disorder, whether chronic or acute, are treated successfully with antibiotics, and although viral conjunctivitis will clear up on its own in 8 to 10 days, antibiotic eyedrops or ointments are often prescribed for most cases of the disease in order to prevent bacterial conjunctivitis. Trachoma, though rare in the United States, is a severe conjunctivitis that can cause loss of vision. Another severe form of conjunctivitis is caused by the gonococcus bacterium and is usually associated with a genital infection. Conjunctivitis in newborn infants, called ophthalmia neonatorum, was a problem at one time; however, routine instillation of silver nitrate solution into the eyes of newborn infants has materially reduced the incidence of blindness.
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