In routine examinations in this age group, the
practitioner performs tests to detect any
tendency to glaucoma. In this
disease, the optic nerve fibres passing through
the small round exit at the back of the eye,
slowly degenerate at a point just before they
exit the eye. This point at the back of the eye
is called the optic disc. It can easily be seen
on routine testing by the eyecare practitioner
who assesses the disc's characteristics in detail.
He may then monitor its appearance at regular
intervals if the disc's appearance raises a
suspicion of early glaucoma. This degeneration
causes gradual loss of vision, often without the
affected person's awareness. The degeneration of
the nerve fibres occurs due to diminished blood
flow at the optic disc, and possibly direct damage to the nerve axons from naked intra-ocular pressure. Degeneration of the tissue supporting the nerve axons due to high IOP, or other factors, can also lead to degeneration of the nerve axons.
This reduction in blood flow is most often
caused by increased pressure within the eye.
However, there are many other possible causes
that are not well understood. These include
vasospasm (abnormal muscle contraction leading to
narrowing of the tiny blood vessels) and other
vascular dysfunctions, cigarette smoking, lowered
blood pressure (especially overnight and when
caused by anti-hypertensive drugs), increased
blood viscosity etc. (normal tension
glaucoma). Future research will
hopefully enlighten us further as to the causes
and possible treatments for poor blood flow at
the optic disc in the presence of normal pressure.
There are many causes of elevated eye pressure.
Some people are clearly genetically disposed to
develop high eye pressure. Another small
proportion of people develop tissue changes
within the eye from other internal eye pathology
that can lead to impaired outflow of the fluid
within the eye. However, many patients who
develop high pressure within the eye, do not show
any obvious causes. My own belief, as well as
that of several authorities in the field, is that
nervous stress plays an important role in
many people who have raised eye pressures.
Other factors, that I have noted to play a
role in raising eye pressure, are coffee (and
possibly non-herbal tea intake), very intensive
close work over long periods of time (without
regular shifting of the focus), obesity, and body
fluid retention (especially as a complication of
certain medication). Unusually high volumes of
fluid intake can also act to raise the eye
pressure. High blood pressure appears to play a
role in some individuals. Patients with
undiagnosed, dangerously high blood pressure can
present with significantly elevated eye pressure.
Eye pressure can be controlled adequately in most
people by medication, surgery or laser treatment.
In checking for glaucoma, the eyecare
practitioner takes the pressure in the eyes and
also looks into the fundus of the eye to check
the health of the optic disc. A pale colour may
signify the onset of glaucoma. Visual fields
testing with automated equipment is performed to
assess the state of the peripheral or side vision.
This is usually the part of one's vision that is
affected first in glaucoma. For further
information on glaucoma you may link with the GLAUCOMA
AUSTRALIA support group.