Keeping an eye out

Glaucoma affects thousands of people of working age every year causing
progressive and irreversible damage to the eyesight. But it is treatable if
spotted in time.  By Catherine Donnelly

Glaucoma is the leading cause of blindness, but half of all people with
damage from glaucoma are unaware of it. Despite the fact that it is roughly as
common as high blood pressure and diabetes, the widespread public lack of
familiarity with the condition results in thousands of cases of blindness
annually, most of which could have been prevented.

Blindness due to glaucoma can usually be prevented if the condition is
detected and treated in time. But patients often have no symptoms in the early stages
and by the time there is visual loss, damage is advanced. Blindness from
glaucoma usually begins with loss of peripheral vision; central vision is
generally maintained until the late stages.

What is glaucoma?

Glaucoma is an eye condition characterised by loss of vision due to damage
to the optic nerve. The optic nerve carries images to the brain and any damage
to the nerve results in impairment of sight. Usually, but not always, glaucoma
is accompanied by increased intra-ocular pressure (IOP) and it is this that
damages the nerve.

Risk factors

Glaucoma has no warning signs. Regular eye examinations and an awareness of
the risk factors provide the best assurance of early detection. The most
important risk factor is high IOP but other risk factors include:

Family history: Approximately 20 per cent of people with glaucoma
have a similarly affected parent or grandparent

Race: Afro-Caribbeans have a higher risk of developing glaucoma

Steroid medication: People who are taking oral or high-dose topical
corticosteroids for more than a few weeks at a time have a higher risk

Age: The risk of glaucoma increases after the age of 40

Diabetes: Diabetes increases the risk by 300 per cent

Eye injury: People who have had an eye injury are at increased risk

Poor vision: People who are extremely nearsighted or farsighted have
an increased risk

How is glaucoma detected?

Ophthalmologists use a variety of tests and instruments to detect symptoms
of glaucoma or early damage caused by this condition. A tonometry test measures
pressure within the eye and a visual field test can detect loss of peripheral
vision. An ophthalmoscope, a small hand-held viewer, and other instruments, are
used to view the interior of the eye and detect damage to the optic nerve.

People who have high IOP but normal peripheral vision and an intact optic
nerve may not require immediate treatment. However, these people are at risk
for developing glaucoma and should be examined every six to 12 months.

Treatment

Treatment, aimed at lowering IOP, can be by surgery, oral medication or
drops, or a combination of these. Drug treatments may have side-effects, such
as blurred vision, but it is important people diagnosed with glaucoma comply
with their treatment regime despite any side-effects, because they will suffer
irreversible loss of vision long before they actually become aware of it.

Types of glaucoma

– Chronic (primary open angle) glaucoma – this form usually
affects both eyes and develops slowly so that loss of sight is gradual. There
is no pain, redness of the eye or dramatic change in vision

– Acute (angle closure) glaucoma – there is a sudden increase
in the IOP in one eye. The eye becomes red and painful and there may be
mistiness of vision and episodes of seeing haloes around lights

– Secondary glaucoma – in this group of conditions an increase
in IOP is caused by other diseases of the eye

– Congenital glaucoma (buphthalmos) – is a condition where
glaucoma is present from birth. An increase in IOP causes the eye to enlarge

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