Glaucoma in the spotlight

Glaucoma is a disease that damages
the eye’s optic nerve.

The optic nerve acts like an
electric cable with more than 1.2 million wires. It is responsible for carrying
images from the eye to the brain.

If the optic nerve fibres are
damaged, the images from this area will not reach the brain and will represent
blind spots in the visual field.

Glaucoma can lead to progressive,
irreversible loss vision if left untreated.

The pressure of the eye also known
as intraocular pressure, or IOP, is controlled by a balance between the
production and drainage of fluid.

The fluid inside the eye is
produced by cells behind the iris (the coloured part of the eye). It passes
through the pupil and leaves the eye through small drainage channels.

These channels are in the angle
between the cornea – the transparent front part of the eye – and the iris.

There are two main types of this
disease: open angle glaucoma and closed angle glaucoma.

Open angle glaucoma – also known as
chronic glaucoma – is by far the most common subtype and accounts for about 90
per cent of all cases. The fluid reaches the drainage channels but they are
slowly clogged over many years.

This is similar to the clogging of
a drainpipe under a sink. The clogging will create a rise in fluid levels
inside the eye and this will in turn make the pressure rise and thereby damage
the optic nerve fibres.

The damage often occurs over many
years without any symptoms or early warning signs. If this is not diagnosed and
treated, the field of vision will gradually become markedly impaired, the blind
spots will spread inwards and outwards leaving only the centre of the field,
so-called “tunnel vision”. In time, even this sight will be lost.

Closed angle glaucoma is also known
as narrow angle glaucoma or acute glaucoma. It is less common and accounts for
about 10 per cent of cases.

This type is very different from
open angle glaucoma in that the pressure usually rises very quickly because the
iris closes the angle and thereby covering the drainage channels, much like a
sink with something covering the drain.

The most common type of angle
closure is seen in people born with narrow angles. The angle will become even
narrower with age because the lens grows through life.

The best treatment for this type of
angle closure can be cataract surgery to create more space in the angles.

Angle closure can be quite painful
and symptoms may include red eye, headache, eye pain, nausea, vomiting, rainbow
coloured rings around lights and blurred vision.

It will cause permanent damage to
the sight if not diagnosed and treated promptly.

Your ophthalmologist can do a
simple test to see if your angle is normal and wide or abnormal and narrow.

Glaucoma is not curable and vision
lost cannot be regained. With treatment, it is possible to halt further loss of
vision. Since glaucoma is a chronic condition, it must be monitored for life.

Risk factors

The main risk factor for developing
chronic glaucoma is the pressure of the eye, either by being too high or by the
optic nerve being vulnerable to even a normal intraocular pressure. Other risk
factors include:

Age: it affects about 1 per cent of
people over 40 years and about 5 per cent of people over 65.

Race: if you are of African
heritage, you have a higher risk of developing glaucoma.

Family: if you have a close
relative with glaucoma, you should visit your ophthalmologist to have your eyes
tested and also advise other family members to do the same.

Diabetes: studies show that
diabetes increases the risk of chronic glaucoma.

Glaucoma is the second leading
cause of blindness in the world, according to the World Health Organisation.

More than three million people are
blind in both eyes because of chronic open angle glaucoma worldwide and more
than two million will develop the disease each year.

Glaucoma is six to eight times more common in
people of African heritage than Caucasians.

African-Americans ages 45-65 are 14
to 17 times more likely to go blind from glaucoma than Caucasians with glaucoma
in the same age group.

Other high-risk groups include: people over
60, family members of those already diagnosed and diabetics.

If you or someone you know worry
about the risk of having glaucoma or just want to have a screening test, call
the Lions Eye Clinic on 244 2818 to make an appointment.

 

Dr. Kjaerbo is a Glaucoma Specialist and Consultant
Ophthalmologist at the Lions Eye Clinic at the Cayman Islands Hospital.

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