What is glaucoma?
Glaucoma refers to a group of eye disorders in which there is damage to the optic nerve (the nerve that sends messages from the eye to the brain). In most cases, this damage is the result of increased pressure in the eye (intraocular pressure). It can lead to loss of vision and even to blindness.
Causes of glaucoma
An area of the eye called the ciliary body produces a fluid (the aqueous humour) that flows through the pupil into the front (anterior) chamber of the eye. Normally, this fluid drains out of the eye into the blood circulation through drainage channels located in the angle between the iris (the coloured part of the eye) and the cornea (the transparent front layer of the eye). If the drainage channels become blocked, then the pressure in the eye builds up, damaging the optic nerve at the back of the eye.
There are 4 main types of glaucoma:
- Chronic open-angle glaucoma (also known as primary open-angle glaucoma) — this is the most common form of glaucoma. The drainage channels narrow down gradually. The only symptom is gradual loss of vision, affecting the peripheral (side) vision first, leading to ‘tunnel vision’. Vision loss can be quite severe before it is noticed.
- Acute angle-closure glaucoma — the drainage angle becomes blocked suddenly by the iris, so that fluid can no longer reach the drainage channels and the pressure in the eye increases rapidly. This causes sudden onset of symptoms that are often severe. If not treated, acute angle-closure glaucoma can rapidly cause vision loss.
- Secondary glaucoma — glaucoma that develops as a result of another disease, such as a cataract, or the use of steroids.
- Congenital glaucoma — a rare form of glaucoma that is present from birth.
Symptoms of acute glaucoma
Symptoms of acute glaucoma include sudden (often severe) eye pain, a red eye, blurred vision, sensitivity to light, and seeing rainbow haloes around lights. The eyeball feels firm and tender. You may also have nausea and vomiting.
Risk factors for acute glaucoma
Acute glaucoma is more common in older people, especially those who are long-sighted, as they often have a narrow drainage angle in their eyes. It is also more common in women than men, and in people with a family history of the condition.
If your eye drainage angles are narrow, then acute glaucoma can be triggered by sudden dilation of your pupils (e.g. because of darkness or stress). The risk of acute glaucoma is also increased by some medicines, including some antihistamines and antidepressants, and rarely, some believe, by certain eyedrops used to dilate the pupils for an eye examination.
Treatment of acute glaucoma
Acute glaucoma is a medical emergency. If you have symptoms of acute glaucoma, you must seek medical attention immediately. If treatment is delayed, there can be permanent loss of vision.
Treatment is usually eye drops and medicines (either by mouth or intravenously — through a drip) to lower the intraocular pressure, followed by laser iridotomy — surgery to open a new channel in the iris to relieve the pressure.
Because people who have had acute glaucoma in one eye are at risk of an acute attack in their other eye, your doctor may suggest surgery to the other eye to prevent this happening.