Webster's New World Medical Dictionary

Lennox-Gastaut syndrome
A severe form of
epilepsy that usually begins in early childhood. It is
characterized by frequent seizures of multiple types,
mental impairment, and a slow spike-and-wave pat-
tern seen on an EEG. The seizures are notoriously
hard to treat and may lead to falls and injuries.
Treatment involves anti-epileptic medications.
lens
The transparent structure inside the eye that
focuses light rays onto the retina.
lens, intraocular
See 
intraocular lens.
lens, objective
In a microscope, the lens nearest
to the object being examined. Most light micro-
scopes now have a turret that bears a selection of
objective lenses.
lens, ocular
In a microscope, the lens closest to
the eye. Also known as eyepiece. Most light micro-
scopes are binocular, with one ocular lens for each
eye.
lentigo maligna melanoma
See 
melanoma,
lentigo maligna.
leprosy
An infectious disease of the skin, nervous
system, and mucous membranes that is caused by
the bacteria Mycobacterium leprae. Leprosy is
transmitted via person-to-person contact. For thou-
sands of years leprosy was one of the world’s most
feared communicable diseases because the nerve
and skin damage often led to terrible disfigurement
and disability. Today leprosy can be cured, particu-
larly if treatment is begun early. Antibiotic therapy is
the mainstay of treatment. Surgery can be per-
formed to reconstruct damaged faces and limbs.
Also known as Hansen’s disease.
leptin
A hormone produced mainly by adipocytes
(fat cells) that is involved in the regulation of body
fat. Leptin interacts with areas of the brain that con-
trol hunger and behavior and signals that the body
has had enough to eat. A small number of people
have genetic mutations in the leptin gene, leading to
a greater demand for food, resulting in obesity.
leptomeninges
The two innermost layers of tis-
sue that cover the brain and spinal cord. The two
layers are called the arachnoid mater and pia mater.