Kids Research Express

Color Blindness, defect of vision affecting the ability to distinguish colors, occurring mostly in males. Color blindness is caused by a defect in the retina or in other nerve portions of the eye. The first detailed report on this condition was written by the British chemist John Dalton, who was himself afflicted with it. Total color blindness, in which all hues are perceived as variations of gray, is known as achromatopsia or monochromatism. This condition is congenital, extremely rare, and affects men and women almost equally. Partial color blindness, called dichromatism, consists generally of the inability to differentiate between the reds and the greens or to perceive either reds or greens; infrequently, the confusion may involve the blues or the yellows. Dichromatism is the most common form of color blindness, affecting about 7 percent of men and less than 1 percent of women. Dichromatism is identified as a sex-linked hereditary characteristic. Color blindness also may occur as a

Trachoma, contagious infection of the eye caused by Chlamydia trachomatis, a bacteria related to the organism that causes psittacosis (disease of birds). Infection is spread by the bite of a host fly. It is a major cause of blindness characterized by hard pustules or granular excrescences on the inner surface of the eyelids, inflammation of the membrane, and subsequent involvement of the cornea. It most commonly occurs among populations living under poor sanitary conditions. The disease begins after an incubation period of five to seven days with inflammation of the eye. Ensuing symptoms are considerable discharge of pus, swelling of the lids, tearing, and increased sensitivity to light. It goes on in a few weeks to chronic swelling, formation of blisters in the eye, and destruction and scarring of the cornea, which eventually causes blindness. In its early stages trachoma responds readily to the topical, and sometimes oral, administration of broad-spectrum antibiotics

Hernia, the protrusion of an organ or part of an organ or other structure through the wall of the cavity that normally contains it. Hernias (incorrectly called ruptures) are qualified by the name of the part that protrudes or the area through which protrusion occurs. Thus, an inguinal hernia, perhaps the most common form, is one that passes through the abdominal wall in the groin area. A diaphragmatic or hiatus hernia is one in which part of the stomach or a loop of the intestine herniates upward through an opening in the diaphragm into the chest cavity. An umbilical hernia is one in which the bowel or the membranous apron overlying it, known as the omentum, protrudes through the abdominal wall under the skin at the navel. Hernias often develop in an area of weakness following unusual stress or strain. An inguinal hernia, for example, may follow the abrupt lifting of a heavy object or a severe bout of coughing. Inguinal hernias are more likely to occur in men than in women because the

Peritoneum, serous membrane in the abdominal cavity. It consists of two layers, a parietal one lining the walls of the cavity and a visceral one closely investing the majority of the abdominal organs, and mooring them firmly in position. Between the two layers there is provision for a space, the peritoneal cavity; in the male this is closed, while in the female there is a direct communication between the sac and the fallopian tubes to enable the ova to reach the cavity of the uterus

Poliomyelitis, infectious viral disease that sometimes results in paralysis. The infection chiefly affects children and young adults and is caused by any one of three related viruses called polioviruses. Doctors diagnose polio by isolating the virus from an infected person using throat cultures, stool samples, or samples of fluids from the brain and spinal cord. Blood tests that indicate the presence of antibodies specific for the virus will also confirm a poliovirus infection. As yet there is no cure for polio—no drug or other medical treatment can halt the destruction of poliovirus in the body. However, several medical treatments can lessen the severity of the disease. Mild cases of polio do not require specific treatment. For the more serious cases of paralytic polio, keeping patients still and quiet can, in some cases, minimize the severity of paralysis. For these patients initial treatment consists of immediate hospitalization and strict bed rest. Simple treatments, including mois

Psychosis, mental illness in which a person loses contact with reality and has difficulty functioning in daily life. Psychotic symptoms can indicate severe mental illnesses, such as schizophrenia and bipolar disorder . Unlike people with less severe psychological problems, psychotic individuals do not usually recognize that their mental functioning is disturbed.

Peritonitis, inflammation of the membrane that lines the abdominal cavity and the organs contained therein. Peritonitis is most often an acute illness, caused by introduction of infection from a perforation of the bowel such as a ruptured appendix or diverticulum. The disease is also caused by introduction of chemically irritating material such as stomach acid from a perforated ulcer or bile from a rupture of the gall bladder or laceration of the liver. Localized peritonitis most often occurs in the pelvis from an infected fallopian tube or a ruptured ovarian cyst. Occasionally peritonitis may occur when the rupture of an abscess causes pus to spill into the abdominal cavity. This sometimes follows surgery inside the bowel with leaking from the site of closure, or from a stab wound through the abdominal wall. Occasionally peritonitis may occur from inflammation of the peritoneal membrane such as in kidney failure, rheumatic fever , and lupus erythematosus . The principal symptom is s