Webster's New World Medical Dictionary

2
Referring to the
macula lutea of the retina.
macular degeneration
Deterioration of the
macula lutea, a common progressive disorder that
causes partial or total loss of macular vision, caus-
ing difficulty in doing tasks that require fine frontal
vision (such as reading and driving a car). Although
some forms of macular degeneration affect young
people, most macular degeneration occurs in peo-
ple over 60 years of age and is termed age-related
macular degeneration (AMD). There are two types
of AMD: the dry type and the less frequent wet type.
In dry AMD, loss of central vision occurs slowly due
to the gradual breakdown of cells in the macula.
Dry AMD may progress to wet AMD, which is some-
times referred to as advanced AMD. Neither type
causes pain. An early symptom of wet AMD is that
straight lines appear wavy. This happens because the
newly formed blood vessels leak fluid under the
macula. The fluid raises the macula from its normal
place at the back of the eye and distorts vision.
Another sign that a person may have wet AMD is
rapid loss of central vision. In both dry and wet
AMD, the person may also notice blind spots. A per-
son who has any of these changes in vision should
consult an ophthalmologist without delay. See also
macular vision.
macular hole
A hole in the macula, the area of
the retina that is responsible for fine central vision.
Macular holes occur mainly in women. In time, cen-
tral vision tends to worsen. A surgical procedure
called vitrectomy (removal of the vitreous humor)
may be considered as a treatment option. See also
macular vision.
macular vision
The type of fine, sharp, straight-
ahead vision that enables people to read, drive, and
perform other activities. As light is focused onto
the macula, millions of cells change the light into
nerve signals that tell the brain what is being seen.
This is called macular or central vision. See also
maculalutea.
macule
A circumscribed change in the color of
skin that is neither raised nor depressed. Macules
are completely flat and can only be appreciated by
visual inspection and not by touch. Physicians refer
to flat skin spots on the skin as macules, as opposed
to papules.
mad cow disease
A nickname for bovine spongi-
form encephalopathy (BSE), a progressive neuro-
logical disorder of cattle that results from infection
by a transmissible agent. The most widely accepted
theory is that the agent is a modified form of a nor-
mal cell surface component known as a prion.
Evidence indicates that BSE has been transmitted to
humans, primarily in the UK, causing a variant form
of Creutzfeldt-Jakob disease (vCJD) and resulting in
degenerative spongiform (soft and full of cavities,
sponge-like) changes in the brain similar to those
seen in affected cattle. Also known as bovine spongi-
form encephalopathy.