Glaucoma is a
group of conditions characterized by
progressive damage to the eye from
increased pressure within the eye,
termed intraocular pressure. [1]
It is a common cause of blindness.
Approximately 2 million Americans
are affected with this group of
disorders, but as much as twenty five percent
of cases remain undetected and
undiagnosed. [2] Glaucoma generally affects the
elderly. However, there are specific
types of glaucoma, like juvenile
and congenital glaucoma, which can
occur in children.
Glaucoma is,
largely, the result of high
intraocular pressure. However, it
does not appear in everyone who has
this condition. Only one percent of
patients who have been diagnosed
with ocular hypertension will also
be subsequently diagnosed with
glaucoma. [1] When elevated intraocular pressure
causes damage to the inner
structures of the eye, including
ntercellular
epithelial edema (swelling) of the
cornea, corneal scarring, necrosis
(tissue death) of the iris, ciliary body stroma, and venous
stasis of the retina, only them is
it diagnosed as glaucoma. [3]
There are two main
classifications of glaucoma:
open-angle and closed angle (or
angle-closure). These categories
refer to the way in which aqueous
outflow is obstructed. [1]
-
In open angle
glaucoma, there is poor
transport of aqueous humor (fluid
in the eye) through the angle in
the anterior chamber of the eye. Even though this angle is open,
the inadequate outflow leads to
elevated pressure in the eye.
This type accounts for 60-70% of
cases of glaucoma.
-
Closed angle
glaucoma refers to an angle
that is obstructed, thereby
preventing adequate outflow,
resulting in the same elevation in
intraocular pressure.
-
Furthermore, some
patients suffer from glaucoma that
is termed "normal or low
pressure glaucoma," in which
case the measured intraocular
pressure is in the normal range
but for some reason in these
patients, the pressure is too high
and they develop glaucoma.
-
Glaucoma can also
be categorized by etiology.
Factors influencing this
categorization include;
developmental glaucoma, glaucoma
associated with inflammation or
injury, and glaucoma following
intraocular surgery.
In addition, glaucoma
can be acute (sudden onset) or
chronic. The majority of cases are
chronic. Persons at a higher risk of
developing open-angle glaucoma
include, as mentioned before, the
elderly, African-Americans,
diabetics, those with a family
history of the disorder, persons who
suffer from hypertension (high blood
pressure), use corticosteroids, or
have myopia. [1]
-
Chronic
open-angle glaucoma is
characterized by a slow
progressive loss of peripheral
vision and later central vision. There are no early warning signs
because by the time an individual starts
demonstrating symptoms, damage
has already occurred. Both eyes
are usually affected, however one
may develop symptoms at a slower
rate than
the other. These patients may
express to their physician
symptoms including; impaired night vision, seeing
halos around lights, mild
headaches, frequent changes in
lenses, and vague visual
disturbances.
-
A patient with
chronic angle-closure glaucoma
generally has no signs and
symptoms until they experience an
attack. Usually only one eye is
affected. The course of this
condition involves recurrent
attacks that start
with seeing halos around lights,
pain in the eye or head, and
episodes of diminished visual
acuity (not being able to see
clearly). These events are
then followed by an attack, characterized by rapid loss of
sight and sudden severe throbbing
pain (often in only one eye),
nausea, vomiting, tearing, and
intense redness. These attacks are also characteristic
of acute angle-closure glaucoma, however these attacks are more
severe and occur more suddenly. Acute angle-closure glaucoma is a
medical emergency and requires
immediate attention, due to the
potentiality
of permanent blindness.
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