CONJUNCTIVITIS

inflammation of the conjunctiva, the delicate mucous membrane that lines the eyelids and covers the front part of the white of the eyethe sclera. The inflammation may be caused by an infection or by a chemical burn or mechanical injury, or it may be part of an allergic reaction. Often both the conjunctiva and the cornea are inflamed, a condition called keratoconjunctivitis. (The cornea is the transparent part of the eyeball in front of the iris and the pupil.) A variety of infectious agents can give rise to conjunctivitis. The microorganism Chlamydia trachomatis is responsible for trachoma, a disease in which the conjunctiva and cornea become scarred, leading to blindness. Trachoma is the most common cause of blindness in the world and is especially prevalent in the Middle East, Asia, and parts of Africa. Inclusion conjunctivitis, so called because of the small bodies that have been observed within (included in) the infected cells, is also caused by C. trachomatis. This disease occurs primarily in newborns who become infected when passing through the birth canal. The viruses of smallpox, chicken pox, and measles also may invade the conjunctiva. Adenoviruses, a group of viruses whose disease-causing members may cause respiratory infections or may survive for long periods in lymphoid tissue (e.g., in the tonsils), may attack the conjunctiva and cornea; the disease is called epidemic keratoconjunctivitis. Bacterial conjunctivitis, also known as pinkeye, is a highly contagious disease of humans and of various domestic animals. The organisms most commonly responsible for bacterial conjunctivitis in humans are staphylococci; pneumococci (Diplococcus pneumoniae organisms); and Haemophilus influenzae organisms, which may invade the respiratory tract or the brain coverings. Gonococcal conjunctivitis, invasion of the conjunctivas by gonorrhea organisms, was once common among newborn infants, who became infected during delivery. This infection can cause blindness if not treated promptly. It is prevented by routine application of a drop of weak silver nitrate solution into each eye of an infant after delivery. Conjunctivitis also may result from an allergic reaction. Phlyctenular keratoconjunctivitis, so called because of the presence of one or more phlyctenulesulcerated, inflamed noduleson the outer part of the cornea, is common among Eskimos. It usually occurs in association with malnutrition or tuberculosis and is thought to be an allergic response to bacteria. Vernal conjunctivitis, or vernal catarrh, is an allergic inflammation that tends to recur in the conjunctivas of susceptible children each year during the summer months and to depart with the coming of cold weather. There are two types of vernal conjunctivitis. In one, the lining of the upper eyelid is affected, with a characteristic red, pebbled appearance. Between the pebbly elevations there is a stringy white substance that has exuded from the mucous membrane. In the second type of vernal conjunctivitis the inflammation, manifested by separate yellowish-pink elevations, is in that part of the conjunctiva that is next to the cornea. A severe form of conjunctivitis that may culminate in blindness occasionally accompanies erythema multiforme, an eruption on the skin and mucous membranes that sometimes occurs in association with a systemic infection, after drug poisoning or the injection of an antitoxin, or during pregnancy.