Dictionary

retinitis pigmentosa and deafness See Usher syndrome.

retinitis pigmentosa A group of inherited disorders in which abnormalities of the photoreceptors (the rods and cones) of the retina lead to progressive visual loss. Abbreviated RP. People with RP first experience defective dark adaptation (night blindness), then constriction of the visual field (tunnel vision), and eventually, late in the course of the disease, loss…

retinal vasculitis Inflammation of the tiny blood vessels of the retina. Retinal vasculitis ranges in severity from mild to severe. Damage to the blood vessels of the retina can cause minimal, partial, or even complete blindness. Retinal vasculitis by itself is painless, but many of the diseases that cause it can also cause painful inflammation…

retinal detachment A separation of the retina from its connection at the back of the eye. The separation usually results from a tear (that is, a rent or rip, not a tear drop) in the retina, which often occurs when the vitreous gel pulls loose or separates from its attachment to the retina. Once the…

retina The nerve layer that lines the back of the eye, senses light, and creates impulses that travel through the optic nerve to the brain. A small area called the macula in the retina contains special light-sensitive cells that allow clear perception and central vision. The retina is filled with tiny blood vessels. See also…

reticulocyte count The number of reticulocytes (young red blood cells) circulating in blood, usually less than 1 percent of the total number of red blood cells. Elevation of the reticulocyte count above 1 percent (reticulocytosis) is a sign of rapid red blood cell production.

reticulocyte An immature red blood cell.

restless leg syndrome An uncomfortable (creeping, crawling, tingling, pulling, twitching, tearing, aching, throbbing, prickling, or grabbing) sensation in the calves that occurs while sitting or while lying down. The result is an uncontrollable urge to relieve the uncomfortable sensation by moving the legs. Restless leg syndrome is a common cause of painful legs. The leg…

resting phase See interphase.

respiratory therapy Exercises and treatments that help patients recover lung function, such as after surgery.

respiratory system The organs that are involved in breathing, including the nose, throat, larynx, trachea, bronchi, and lungs. Also known as the respiratory tree.

respiratory syncytial virus A virus that causes mild respiratory infections, colds, and coughs in adults and can produce severe respiratory problems, including bronchitis and pneumonia, in young children and anyone with compromised immune, cardiac, or pulmonary systems. Abbreviated RSV. RSV is spread via respiratory secretions and is highly contagious. Infections usually occur during annual community…