Glaucoma is a condition in which the nerve of the eye (optic nerve) is damaged by high pressure inside the eye. About 4% of the population has glaucoma and it is most common after the age of 40. It sometimes runs in families (may be inherited), so family members of patients with glaucoma should be examined.
Vision lost as a result of glaucoma cannot be recovered, but early diagnosis and careful life-long treatment can prevent further vision loss. Glaucoma is an insidious condition and usually no symptoms are present, so it can only be diagnosed by a full eye examination.
What causes glaucoma?
Fluid is continually produced inside the eye to nourish the structures within it. This fluid normally drains out of the eye at the same rate as it is produced through tiny drainage canals. This maintains a steady pressure within the eye. We refer to this pressure as the
intraocular pressure and this pressure is normally is between 10 - 21 mmHg.
In patients with glaucoma, the fluid is unable to drain out through the outflow canals at the normal rate as they are partially blocked. As a result the intraocular pressure increases and with time this damages the optic nerve. This in turn leads to gradual loss of vision.
How can damage be detected?
The early vision changes are very slight and do not affect the central vision (the central portion of what you see when looking straight ahead or reading). However parts of the peripheral vision (top, sides and bottom areas) may be affected and the patient will not notice this until severe loss has occurred.
Damage to the eye can be detected by examining the optic nerve. The ophthalmologist will look through the pupil to examine the nerve, which has the appearance of a small white disc (1.5mm diameter) with blood vessels emerging from its centre. It is normal for the nerve to have a slight central excavation. With progression of glaucoma and damage to the nerve fibres, this excavation or cupping increases.
New technology using Ocular Coherence Tomography (OCT) is now available. This can examine the optic nerve, the nerve fibre layer and other cellular layers in the retina to detect damage before this can be detected with other tests
As glaucoma progresses, you can start to loose parts of your peripheral vision, and you can get small blind spots in your central vision. These can be detected by doing a visual field test. Visual field testing is a sophisticated computerised test that maps your whole field of vision. On the printout the lightly shaded areas indicate where you can see, and the dark areas indicated where vision has been lost. This is a very important test in helping to diagnose and monitor glaucoma, and needs to repeated at least once a year.
How is glaucoma treated?
There is no cure for glaucoma but the condition can be controlled. The primary treatment is eye drops to reduce the intraocular pressure. This is a constant life-long treatment and the drops need to be taken regularly to be effective.
When inserting eye drops, lean your head back, look upwards and pull the lower lid down. Gently squeeze the bottle so that one-drop goes into the space between your lower lid and the eyeball. Then close your eye for 30 seconds. Do not touch the tip of the bottle on the eye or lashes. Sometimes more than one type of eye drop may be required in which case you should wait 5 minutes before inserting the second drop.
Make your medications part of your daily routine. If you forget to use your eye drops, administer a drop as soon as you remember rather than waiting until the next scheduled time.
If further vision loss occurs despite the regular use of eye drops, laser treatment or surgery may be required.
Normal tension glaucoma
It is possible to have a type of glaucoma with all the typical features except that the intraocular pressure remains within the normal range. This occurs if the optic nerve is more vulnerable than normal due to poor circulation in the nerve. The treatment remains the same - drops or surgery will be used to reduce the pressure.