GLAUCOMA
Glaucoma is an eye disease in which the optic nerve
- the part of the eye that carries the images we
see to the brain - is damaged. The optic nerve contains
many small nerve fibers that are very sensitive to
pressure changes inside the eye. If the intra-ocular
pressure (pressure inside the eye) exceeds a critical
level (which may be different for each person), damage
to the optic nerve begins. Once destroyed, these
nerve fibers cannot regenerate. This can lead to
permanent vision deficits such as blind spots, visual
field defects or even complete blindness. Early detection
and control of intra-ocular pressure are the keys
to preventing optic nerve damage and blindness from
glaucoma.
CAUSES OF GLAUCOMA
There is a fluid produced by a part of the iris
called the ciliary body that fills the front portion
of the eye (the anterior chamber). This fluid is
known as the aqueous humor. Aqueous humor is produced
at a constant rate by the ciliary body, where it
circulates through the anterior chamber then flows
out of the eye at the same rate through the drainage
angle (area between the iris and cornea). This steady
state of aqueous humor flow keeps the pressure in
the eye relatively constant. If, however, the rate
of flow out of the eye decreases (from blockage of
the drainage angle), the continual influx of aqueous
humor will cause the pressure inside the eye to increase
potentially, causing damage to the optic nerve.
TYPES OF GLAUCOMA
The type of glaucoma is related to the way in which
the drainage angle is blocked. Chronic open-angle
glaucoma, the most common form, arises when the drainage
angle becomes inefficient at allowing fluid flow
from the eye. The pressure gradually increases over
time, and damage to the optic nerve is slow and progressive.
The damage is so slow and painless that there are
no noticeable symptoms until the optic nerve is significantly
damaged. The risk of open-angle glaucoma increases
with age, and treatment is aimed at lowering the
intra-ocular pressure through eye drops, laser or
surgery.
The other type of glaucoma, angle closure glaucoma,
occurs when the drainage angle is completely blocked
by the iris. This can cause a sudden increase in
intra-ocular pressure leading to blurred vision,
severe eye pain, headache, nausea or vomiting and
halos (colored) around lights. This is known as an
acute angle-closure attack, and represents a true
eye emergency. Blindness from this type of glaucoma
can occur rapidly, sometimes within hours if not
treated. Angle-closure glaucoma is seen more often
in people with smaller (farsighted) eyes and those
of Caucasian heritage, but is relatively uncommon
with respect to chronic open angle glaucoma. Treatment
usually involves laser surgery and eye drops.
RISK OF GLAUCOMA
Although there are many factors that contribute
to the risk or likelihood of developing glaucoma,
the three with the most significance include, age,
family history and past eye injuries. But everyone,
despite presence or absence of risk factors, should
be screened for glaucoma regularly.
DETECTION OF GLAUCOMA
The best way to detect glaucoma is with regular
eye examinations by an ophthalmologist. Complete
evaluation should include dilated examination of
the retina (ophthalmoscopy), inspection of the drainage
angle (gonioscopy), measurement of intra-ocular pressure
(tonometry), measurement of the corneal thickness
(pachymetry) and testing of the peripheral visual
field of each eye (perimetry). All are necessary
to detect and treat glaucoma.
TREATMENT OF GLAUCOMA
Treatment depends on the type and severity of the
glaucoma and may include eye drops, laser or surgery.
All are aimed at lowering the pressure and preserving
optic nerve function and vision.
More information:
http://www.medem.com/medlb/articleslb.cfm?sub_cat=2012
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