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How
is glaucoma diagnosed?
The
early detection of glaucoma is key to controlling
its progression and preventing further damage. In
order to detect symptoms, your eye doctor will perform
a routine eye examination including tests aimed
at measuring the pressure in your eyes (tonometry),
evaluating the appearance of your optic disk (funduscopy),
and checking for the presence of any loss in peripheral
vision (visual field testing).
Here is a small tip! It is important to note
that your doctor may administer drops in one or
both of your eyes to dilate your pupils as part
of the examination. This can result in the temporary
blurring of your vision. It is advisable that
you have someone accompany you to your appointment.
Tonometry
The tonometer is a machine used in the measurement
of intraocular pressure (IOP). It determines the
resistance of the eyeball to indentation by an
applied force. The air-puff tonometer is one of
several types of tonometers and can commonly be
found in many eye doctors' offices. It does not
touch the eye but ejects a small puff of pressurized
air in order to detect any abnormal levels of
IOP.
IOP reflects the balance between the production
and elimination of aqueous humor in the eye. In
the general population, the normal range for IOP
is 15.8 ± 2.5 mmHg.
Funduscopy
Your eye doctor may want to examine the interior
of your eye, specifically, your optic nerve. An
instrument called an ophthalmoscope studies the
back of your eye (the fundus) through the pupil,
enabling the eye doctor to assess for the presence
of damage, such as cupping, around the optic nerve.
In the normal eye, the optic cups are symmetric,
and the rim of the optic nerve is pink. With glaucoma,
either a generalized enlargement or notching of
the optic cup can be seen. The rim remains pink
until late stages of the disease but is thinner.
Visual Field Testing
Your eye doctor may want to check for the presence
of any loss of visual field, which is often an
indication of a damaged optic nerve. In addition,
glaucoma often produces characteristic changes
in your visual field, such as a generalized shrinking
of your range of vision. A two-dimensional tool
with intersecting vertical and horizontal lines
is commonly used to discover such a visual field
defect. A kinetic visual field test, for example,
consists of an object that moves around the grid.
The patient is asked to specify where he/she can
see the object, and where he/she cannot, thus
enabling the doctor to establish the boundaries
of the patient's field of vision.
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