Webster's New World Medical Dictionary

367
restless leg syndrome
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cause of painful legs. The leg pain typically eases
with motion of the legs and becomes more notice-
able at rest, worsens during the early evening or
later at night, and may cause insomnia.
retardation, mental
See 
mental retardation.
retardation, reading
See 
reading retardation.
reticulocyte
An immature red blood cell.
reticulocyte count
The number of reticulocytes
(young red blood cells) circulating in blood, usu-
ally 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.
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 
eye.
retinal detachment
A separation of the retina
from its connection at the back of the eye. The sep-
aration 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 sepa-
rates from its attachment to the retina. Once the
retina has torn, the vitreous liquid can pass through
the tear and accumulate behind the retina. The
build-up of fluid behind the retina is what separates
(detaches) the retina from the back of the eye.
Vision loss occurs if the detached retina is not
repaired.