What is glaucoma?
Glaucoma is an umbrella term for a number
of conditions that cause a build up of fluid pressure in the eye, damaging the
optic nerve and the nerve pathways of the retina.
The fluid in the eye is constantly being
drained and refreshed. Pressure occurs when the drainage channels, called the
trabecular meshwork, become blocked or obstructed. This can be caused by a
blockage within the channels, or by pressure on the channels from exterior
sources, such as enlarged blood vessels.
There are main four types of glaucoma:
Chronic open-angle glaucoma.
Primary angle-closure glaucoma.
Developmental glaucoma – this occurs in
babies and children.
Who does glaucoma affect?
It is estimated that there are more than
half a million people in the UK with glaucoma, with around 2% of the population
over the age of 40 affected and as many as 10% of over the age of 75. Most of
these cases will be chronic open-angle glaucoma. People of black African or
black-Caribbean origin are more likely to have chronic open-angle glaucoma,
while people of Asian origin are more prone to acute closed-angle glaucoma.
Your risk of developing glaucoma is
increased by a range of factors including short sightedness, family history of
glaucoma and diseases such as diabetes and ocular hypertension.
What are the symptoms of glaucoma?
The symptoms vary depending on the specific
type of glaucoma that you have. The most common type, chronic open-angle glaucoma,
develops very slowly, starting with a gradual loss of peripheral vision. In
this case, glaucoma may not be noticed until it has reached an advanced stage
and begins to affect the centre of the visual field. Since this damage is
irreversible, it is important to have regular eye examinations to detect
glaucoma as early as possible.
By contrast, acute angle-closure glaucoma
causes a range of severe, sudden onset
Eye redness and tenderness.
Star bursts around bright lights.
Misty vision or vision loss.
These symptoms may only last for a few
hours, but you should seek medical help immediately as each ‘attack’ will
damage your sight a little more. Secondary glaucoma can often cause similar
symptoms. However in this case, the glaucoma is itself a symptom of another eye
condition, such as uveitis or an injury to the eye.
How is glaucoma diagnosed?
Glaucoma is usually detected during a
routine eye examination. Your optician will test your peripheral vision to
check for any blind spots that may indicate nerve damage. He or she will also
examine your eye in detail, checking the pressure in the eye, the thickness of
your cornea and the condition of your optic nerve and the front outer edge of
your eye where the drainage normally takes place.
The most common forms of glaucoma develop
very slowly, often without you noticing, so it is crucial that you have your
eyes examined at least every two years. Since any damage caused by glaucoma is
irreversible, the sooner it is diagnosed and treated the better.
Treatment for glaucoma
Several treatments are available, depending
on the type of glaucoma and how advanced the condition has become. Initially,
you are likely to be prescribed eye drops. These include:
Prostaglandin analogue drops, which
increase the fluid flow and reduce the pressure in your eye.
Beta blockers, which reduce the rate at
which fluid is produced in your eye.
Carbonic anhydrase inhibitors, which also
reduce the rate at which fluid is produced.
Sympathomimetics, which both reduce
production and increase the flow rate.
Laser surgery may be used to treat
glaucoma, either by physically opening up the trabecular meshwork by making
small holes to increase drainage (laser trabeculoplasty) or by destroying part
of the tissue that produces the fluid (cyclodiode laser treatment).
Non-laser surgery can also be used to treat
glaucoma. Different techniques are possible, each designed to improve drainage
and reduce intra-ocular pressure:
Trabeculectomy. This procedure which makes
a small hole in the sclera to assist in drainage.
Deep sclerectomy. Surgery makes a small
area of the sclera thinner so that fluid can escape.
Aqueous shunt implant. A device is
implanted to drain fluid away to a small reservoir behind the eye from where it