Overview
The eye is filled with fluid that is made and drained continuously. If the fluid cannot drain freely, the pressure inside the eye rises and presses on the optic nerve, the cable that carries images from the eye to the brain. Glaucoma is the damage that follows.
In the common open-angle type the drainage becomes gradually less efficient and the pressure creeps up over years. In angle-closure glaucoma the drainage angle blocks, sometimes suddenly, and the pressure rises in hours. Some people develop nerve damage even with a pressure that reads normal, which is why the nerve itself, and not only the pressure, is examined.
Symptoms
The usual, slow form has no symptoms at all in its early years. When damage is advanced, the first thing noticed is often bumping into door frames or missing things to the side, because vision is lost from the edges inwards. Central, reading vision goes last.
A sudden angle-closure attack is entirely different and unmistakable:
- Severe pain in and around one eye
- A red eye
- Blurred or misty vision
- Rainbow-coloured rings or halos around lights
- Severe headache
- Feeling sick, or vomiting
When to see a doctor
Arrange an eye check in the next few days if you are bumping into things or notice gaps in your vision, if an eye test has reported raised pressure, if glaucoma runs in the family and you have not been examined, or if glaucoma drops have run out.
Causes
Most glaucoma happens because the eye's drainage channels work less and less well with age, so pressure builds slowly. Nobody can say why this begins in one person and not another.
Secondary glaucoma follows another problem in the eye: an injury, long-standing inflammation, an advanced cataract, diabetes that has damaged the blood vessels of the eye, or the long term use of steroid medicines, including steroid eye drops bought without a prescription. A rare form is present from birth and shows as watery, cloudy, light-sensitive eyes in a baby.
Risk factors
- Age, with the risk climbing from around fifty onwards
- A parent, brother or sister with glaucoma
- Raised pressure inside the eye
- Diabetes
- Being very short-sighted or very long-sighted
- A previous injury or operation on the eye
- Long term use of steroid medicines or steroid eye drops
- African, Caribbean or Asian family origins
Complications
Untreated glaucoma narrows the field of vision until only a small central island is left, and eventually that goes too. The loss is permanent, because the nerve fibres that die are not replaced. Glaucoma is one of the leading causes of irreversible blindness worldwide.
Even before sight is lost completely, a narrowed field makes driving unsafe, raises the risk of falls, and makes moving about in poor light difficult. An untreated angle-closure attack can take the sight of that eye within a day or two.
Prevention
Glaucoma cannot be prevented, but the blindness it causes very often can, simply by finding it early.
- A full eye test every one to two years from around the age of forty, and every year with diabetes or a family history
- Telling the optician or eye doctor if anyone in the family has glaucoma
- Never using steroid eye drops without a prescription and without follow up
- Keeping diabetes and well controlled
- Wearing eye protection for work or sport that can injure the eye
- Using prescribed drops exactly as directed, and never stopping them because the eye feels fine
Diagnosis
Glaucoma is usually found at a routine eye test, before it causes symptoms. Several checks are done together, because no single one is enough.
- Measuring the pressure inside the eye
- Examining the optic nerve head through widened pupils, often with a scan that measures the nerve fibre layer
- A visual field test, which maps the side vision and picks up gaps the person has not noticed
- Looking at the drainage angle with a special lens
- Measuring the thickness of the cornea, which affects how the pressure reading is interpreted
Treatment
All treatment works by lowering the pressure inside the eye. It protects what sight remains, and it does not bring back what has gone.
- Eye drops, usually the first treatment, used every day for life unless the doctor changes them
- Laser treatment, to help fluid drain better or to open a blocked angle
- Surgery to create a new drainage route, or to insert a small drainage device, when drops and laser are not enough
- Cataract surgery, which in some angle-closure eyes also lowers the pressure
- Urgent medicines and laser for an acute angle-closure attack, often followed by treatment of the other eye to prevent the same thing happening there
Follow up continues for life, with the pressure and the visual field rechecked at intervals, because the treatment has to keep pace with the disease.
Myths and facts
Things people often say about this. Open each one to see what is true.
Myth“Kala motia and safed motia are the same thing, and an operation will bring the sight back.”What is true?
Fact
They are different conditions. Cataract, safed motia, is a clouding of the lens, and surgery to replace the lens usually restores clear vision. Glaucoma, kala motia, damages the optic nerve. Treatment can stop the damage going further, but sight already lost to glaucoma cannot be recovered.
Myth“My vision is fine, so my eyes cannot have glaucoma.”What is true?
Fact
The common form of glaucoma causes no symptoms for years. Side vision goes first, and the other eye covers the gap, so the loss is not noticed. It is usually picked up on a routine eye test before it causes any trouble, which is the whole point of having one.
Myth“Once the pressure has come down, the drops can be stopped.”What is true?
Fact
The drops lower the pressure only while they are being used. Stopping them lets the pressure rise again and the nerve damage continue, usually without any symptom to warn you. Drops are changed or stopped only by the eye doctor.
Myth“Glaucoma always hurts, so a painless eye is a healthy eye.”What is true?
Fact
Most glaucoma is completely painless. Severe pain happens in the sudden angle-closure type, where the drainage angle blocks abruptly, and that is an emergency. A painless eye tells you nothing about the pressure inside it.
Myth“Once glaucoma is found, going blind is only a matter of time.”What is true?
Fact
That is not the usual outcome. When glaucoma is found and treated, and the drops or procedures are kept up and the eyes checked regularly, most people keep useful sight for the rest of their lives.
Questions to ask your doctor
Tick the ones you want answered and take them with you.
Common questions
The doctor says my eye pressure is high but I do not have glaucoma. What does that mean?
It means the pressure is above average but the optic nerve and the visual field are still normal. This is often called ocular hypertension. Some people with it go on to develop glaucoma and some never do, so the eye doctor either watches it at regular intervals or starts drops, depending on how high the pressure is and what other risks are present.
If glaucoma runs in my family, when should I get checked?
Sooner than other people. Tell the eye doctor about the family history and ask when to start and how often to return. A brother or sister of someone with glaucoma is at higher risk than the general population, and checks are usually advised yearly from around the age of forty.
Are the eye drops safe to use for years?
They are used for years precisely because glaucoma is lifelong. Some cause stinging, redness, a change in eyelash growth or a darkening of the iris, and a few can affect the heart rate or breathing in people with asthma or heart conditions. Tell the eye doctor about your other illnesses and medicines, and report any new symptom rather than stopping the drops yourself.
Can I still read, watch television and use a phone with glaucoma?
Yes. Reading and screen use do not make glaucoma worse, and central vision is usually the last thing affected. Dim light and glare can be harder to cope with as the field narrows, so good lighting helps. What does matter is using the treatment and keeping the follow up appointments.
