Myopia, which tends to be inherited,
usually appears around puberty and
increases until the early 20s. If it starts
in early childhood it may become very
severe. The condition is detected during
a vision test. Treatment is with concave
glasses(or contact lenses) or by photo-
refractive keratectomy.
myosinA major protein component of
musclefibres. Together with actin, it
provides the mechanism for muscles to
contract. The myosin molecules slide
along the actin filaments to make the
muscle fibres shorter.
myositisInflammation of muscletissue,
causing pain, tenderness, and weak-
ness. Types of myositis include myositis
ossificans(in which damaged muscle is
replaced by bone), polymyositis, and
dermatomyositis.
myositis ossificansA congenital or
acquired condition in which bone is
deposited in muscles. The congenital
form is rare. The first symptoms are
painful swellings in the muscles, which
gradually harden and extend until the
affected child is encased in a rigid sheet.
There is no treatment, and death results.
The acquired form may develop after
a bony injury, especially around the
elbow; it causes severe pain and a
swelling, which hardens. Treatment with
diathermy, coupled with gentle, active
movements, may be helpful.
myotomyA surgical procedure that in-
volves cutting into a muscle.
myotoniaInability of a muscleto relax
after the need for contraction has
passed. It is a feature of myotonic dys-
trophy, a form of muscular dystrophy.
myringitisInflammation of the ear-
drum. Myringitis occurs in otitis media.
myringoplastySurgical closure of a
perforation (hole) in the eardrum (see
eardrum, perforated) by means of a tis-
sue graft (see grafting).
myringotomyA surgical opening made
through the eardrum to allow drainage
of the middle-ear cavity. It is usually
performed to treat persistent glue earin
children. A grommetmay be inserted
into the eardrum at the same time.
myxoedemaA condition in which there
is thickening and coarsening of the skin
and other body tissues (most noticeably
in the face). Myxoedema is usually due
to hypothyroidism; in such cases, the
condition is commonly accompanied by
weight gain, hair loss, sensitivity to
cold, and mental dullness. The term
“myxoedema” is sometimes used for
adult hypothyroidism.
myxomaA noncancerous, jelly-like tu-
mourcomposed of soft mucous material
and loose fibrous strands. Myxomas us-
ually occur singly, and may sometimes
grow very large. They may develop under
the skin, in the abdomen, in the bones,
or, very rarely, inside the cavities of the
heart. In this case, thrombi (blood
clots) may form, and the flow of blood
through the heart may be obstructed.
Myxomas can usually be successfully
removed by surgery.MYOSIN MYXOMA
M