Glaucoma – Types, Causes, Symptoms, Treatment and Screening

Raised pressure of fluid within the eye that affects vision and can end in blindness. It occurs in 1% of the population.

Acute Glaucoma

Normally, the fluid that is secreted into the front of the eye to maintain the eye’s shape and nourish the tissues drains away continuously However, in acute glaucoma, the drainage system suddenly develops a blockage, and the fluid pressure inside the eye rises rapidly, causing pain and a “red eye”. Acute glaucoma is a medical emergency. Without prompt treatment, the eye can swiftly become damaged and a permanent reduction in vision can result. Acute glaucoma is rare under the age of 40 and most common over the age of 60. The tendency to develop it sometimes runs in families.

Chronic Glaucoma

Chronic glaucoma is a gradual, painless increase in the fluid pressure inside the eye, usually starting after the age of 40 and sometimes running in families. It is more common in people of african descent Chronic glaucoma is also known as open-angle glaucoma. The condition causes a gradual deterioration of sight due to a progressive build-up of fluid pressure inside the eye over a period of several years.

There are often no symptoms until late in the disease, and loss of vision is permanent. Although the condition can lead to total blindness, early treatment can prevent severe damage. In most cases, both eyes are affected, although symptoms may only occur in one eye initially.

Causes of Glaucoma

There is a circulation of fluid, called aqueous humour, within the eyes, between the cornea and the lens. This fluid is continually being produced and normally drains through channels at the edge of the iris – the coloured portion of the eye. In many people this drainage system deteriorates with age, ultimately resulting in increased pressure of fluid. This is chronic glaucoma. Acute glaucoma is a type of glaucoma where the drainage is abruptly obstructed, causing sudden symptoms; fortunately acute glaucoma is rare.

Glaucoma affects vision by damaging the optic nerve where it leaves the back of the eyeball. This causes a loss of the outer (peripheral) field of vision. Unless it is treated, deterioration continues until blindness occurs.

People who use steroid eye drops for long periods of time may develop glaucoma. Some drugs, for example antidepressants and certain drugs prescribed for Parkinson’s disease, worsen pre-existing glaucoma by widening the iris, thereby reducing drainage of fluid. There is also a strong family tendency to glaucoma.

Causes of Acute Glaucoma

The fluid in the front part of the eye is produced continuously by a ring of tissue called the ciliary body, behind the eye’s coloured iris. Normally the fluid flows out through the pupil and drains away through the sieve-like meshwork behind the drainage angle at the outer rim of the iris. In acute glaucoma, the iris bulges forwards and closes the drainage angle, so that fluid is trapped within the eye. The pressure inside the eye rises as more fluid is secreted and as the pressure rises, it may damage the optic nerve, which carries nerve signals to the brain, causing reduced vision.

Symptoms of Glaucoma

Early glaucoma does not produce any noticeable symptoms. Even though peripheral vision is being lost, the brain compensates as long as central vision remains good. However, at night, when pupils are dilated to a maximum, fluid drainage is reduced. People may notice haloes around lights and there may be slight discomfort in the eye.

Acute glaucoma causes dramatic symptoms – sudden blindness or extremely hazy vision, the eyeball is intensely painful and red and the normally clear cornea becomes cloudy. Increased pressure within the eyeball makes it feel very hard.

Symptoms of Acute Glaucoma

Mild attacks of acute glaucoma tend to occur in the evening when you are tired, and
symptoms include pain in the eyes and haloes appearing around lights. Sleeping usually
relieves these symptoms. Full-blown attacks develop suddenly and include these symptoms:

• rapid deterioration of vision
• intense pain in the eye
• redness and watering of the eye
• sensitivity to bright light
• haloes appearing around lights
• nausea and vomiting.

Symptoms of Chronic Glaucoma

By the time symptoms appear, it is probable that your vision has been permanently affected. At this late stage, symptoms may include:

• bumping into objects because of loss of the outer edges of vision (peripheral vision)
• blurring of objects that are straight ahead of you.

Screening of Glaucoma

The best way to detect early glaucoma is with regular tests of the field of vision using special charts. There is a screening test where air is directed at the eyeball, depressing it briefly; pressure within the eye is calculated from the degree of depression. A more accurate measure is by applying a pressure gauge to the eyeball under local anaesthetic. Glaucoma causes characteristic appearances at the back of the eye as seen through an ophthalmoscope.

Treatment of Glaucoma

Chronic glaucoma is controlled with eye drops that reduce the pressure within the eye. Some drugs reduce the rate of production of the aqueous humour fluid, thereby keeping pressure low. Other drugs keep the pupil constricted and drainage at a maximum. Similar treatment is used for acute glaucoma, with higher doses and sometimes using drugs taken by mouth. When surgery is required, it involves cutting the edge of the iris with a small scalpel or laser to improve drainage.

Treatment of Acute Glaucoma

Applanation tonometry, which measures the pressure inside the eye, is used to detect acute glaucoma. Laser iridotomy is usually performed to correct the condition.

Laser Iridotomy

This technique is used to treat acute glaucoma, in which pressure in the eye rises suddenly due to blockage in the outflow of fluid. First, the pressure is reduced using eye drops, intravenous drugs and, possibly, oral drugs. Anaesthetic eye drops are then put into the eye, and a thick contact lens is placed in front of it to focus a laser beam onto the bulging iris. The laser cuts a small hole in the iris, releasing the fluid behind it. The iris flattens, opening the drainage angle and letting trapped fluid flow out. The hole remains in the iris, harmlessly.

Treatment of Chronic Glaucoma

• If chronic glaucoma is diagnosed early, eye drops to reduce the pressure in the eye will probably be prescribed. You will probably have to continue using these eye drops for the rest
  of your life.
• If the condition is advanced, or if eye drops do not lower the pressure sufficiently, surgery
  may be needed to make a drainage channel in the white of the eye.
• In another surgical technique, called laser trabeculoplasty, a laser beam is used to
  increase the flow through the trabecular meshwork, allowing fluid to drain away.

Questions

When should people be screened?

If you have a close relative (for instance a parent or a sibling) with glaucoma you should be screened every three years from the age of forty onwards – the condition runs in families. Everyone else should see their optician for an eye check specifically for glaucoma when they reach sixty

Can glaucoma be cured?

There is no permanent cure for glaucoma, but drugs can help to control the condition. Even after surgery you will need to see an ophthalmologist regularly.

Risks Factors

• Having an eyeball that is smaller than normal is a common cause of farsightedness and increases the risk of developing acute glaucoma.
• The disorder is more common in older people because the lens of the eye thickens
  throughout life and may eventually press against the iris. Fluid then builds up behind
  the iris, which bulges forwards and blocks the drainage angle.
• Occasionally, acute glaucoma may be triggered when dim light causes the pupil to
  widen. The iris then thickens and the drainage angle can close.
• Acute glaucoma sometimes runs in families.

Complementary Treatment

Warning: Never use aromatherapy oils near the eyes. Acute glaucoma is a medical emergency — see your doctor immediately. Complementary therapies provide options for long-term glaucoma. A nutritional therapist might recommend cutting down on protein and/or supplementing vitamins A, B, and C, and the minerals chromium and zinc. Other therapies to homoeopathy; reflexology; naturopathy; yoga.