Glaucoma is a disease of the major nerve of vision, called the optic nerve. The optic nerve receives light from the retina and transmits impulses to the brain that we perceive as vision. Glaucoma is characterized by a particular pattern of progressive damage to the optic nerve that generally begins with a subtle loss of side vision (peripheral vision). If glaucoma is not diagnosed and treated, it can progress to loss of central vision and blindness. Glaucoma is usually, but not always, associated with elevated pressure in the eye (intraocular pressure). Generally, it is this elevated eye pressure that leads to damage of the eye (optic) nerve. In some cases, glaucoma may occur in the presence of normal eye pressure. This form of glaucoma is believed to be caused by poor regulation of blood flow to the optic nerve.

Complications of Glaucoma
If left untreated, glaucoma will cause progressive vision loss, typically in these stages:

• Blind spots in your peripheral vision
• Tunnel vision
• Total blindness

Causes of Glaucoma

Glaucoma is caused by an increase in pressure within your eye or a weakness in the optic nerve, or both. You're more likely to get glaucoma later in life. Not many people under 40 will develop the condition, but two in 100 people over the age of 40 and five in 100 people over the age of 70 will develop some type of glaucoma.

Other factors that can increase your chances of getting glaucoma include:

• ethnicity - if you're of African or black Caribbean origin, you're more at risk and it may affect you earlier in life and be more severe
• family history - if you have a close relative with glaucoma, it's important to have regular eye tests from the age of 35
• being very short-sighted
• diabetes

Signs & Symptoms of Glaucoma

The most common types of glaucoma — primary open-angle glaucoma and acute angle-closure glaucoma — have completely different symptoms.

Primary open-angle glaucoma signs and symptoms include:

• Gradual loss of peripheral vision, usually in both eyes
• Tunnel vision in the advanced stages
• Acute angle-closure glaucoma signs and symptoms include:
• Severe eye pain
• Nausea and vomiting (accompanying the severe eye pain)
• Sudden onset of visual disturbance, often in low light
• Blurred vision
• Halos around lights
• Reddening of the eye

Both open-angle and angle-closure glaucoma can be primary or secondary conditions. They're called primary when the cause is unknown and secondary when the condition can be traced to a known cause, such as eye injury, inflammation, tumor, or advanced cataract or diabetes. In secondary glaucoma, the signs and symptoms can include those of the primary condition as well as typical glaucoma symptoms.

Diagnosis of Glaucoma

These are some of the tests that can establish a diagnosis of glaucoma:

• Tonometry. Tonometry is a simple, painless procedure that measures your intraocular pressure, after numbing your eyes with drops. It is usually the initial screening test for glaucoma.
• Test for optic nerve damage. To check the fibers in your optic nerve, your eye doctor uses an instrument that enables him or her to look directly through the pupil to the back of your eye. This can reveal slight changes that may indicate the beginnings of glaucoma.
• Photographs and drawings of the optic nerve. These images may be useful for documenting the severity of the condition.
• Visual field test. To check whether your visual field has been affected by glaucoma, your doctor uses a special test to evaluate your peripheral (side) vision.
• Pachymetry. Your eyes are numbed for this test, which determines the thickness of each cornea, an important factor in diagnosing glaucoma. If you have thick corneas, your eye pressure reading may read artificially high even though you may not have glaucoma. Similarly, people with thin corneas can have normal pressure readings and still have glaucoma.
• Other tests. To distinguish between open-angle glaucoma and angle-closure glaucoma, your eye doctor may use a technique called gonioscopy in which he or she places a special lens on your eye to inspect the drainage angle. Another test, tonography, can measure how quickly fluid drains from your eye.

Treatments of Glaucoma

Treatment for glaucoma aims to lower the pressure inside your eye to reduce the risk of future sight loss if it hasn't already deteriorated, or prevent any further loss of sight. Treatment can't reverse any existing optic nerve damage, so it won't improve your sight if it has already deteriorated.

Options include medicines given as eye drops, laser treatment and surgery.

Medicines

There are different types of eye drops available for treating glaucoma. These include:

• prostaglandin analogues that help your eye's internal fluid drain out more quickly
• beta-blockers that reduce the pressure in your eye - they slow down the build-up of fluid by reducing production of it

Several other types of medicine are available in drop and tablet form, as alternatives or in addition to beta-blockers or prostaglandins. It's important that you use any prescribed eye drops every day as advised by your doctor to ensure consistent lowered pressure in the eye. If you don't, the pressure in your eye will rise again.

There are different side-effects for each type of medicine. Ask your doctor or pharmacist for more information. If you think your medicine is causing a side-effect, speak to your doctor as soon as possible. He or she can advise you and if necessary can prescribe a different drop or consider other treatments.

Surgery

• Laser treatment

A laser can be used to open the holes in the draining system to help fluid drain out of your eye or stop your eye producing as much fluid.

The procedure is usually quick and causes little discomfort. It can be done under local anaesthesia and you will be able to go home the same day. The success of this type of treatment varies from person to person, and you may need to continue using eye drops after laser treatment.

• Trabeculectomy surgery

You may be able to have surgery if medicines and/or laser treatment haven't lowered the pressure in your eye.

There are a range of operations and the most commonly performed is trabeculectomy. In this operation a tiny opening is created in your eye wall to allow fluid to escape under the thin lining of the white of your eye (the conjunctiva) and be absorbed back into your bloodstream. You may have the operation under local or general anaesthesia.

Prevention of Glaucoma

• Get regular eye care. Regular checkups can help detect glaucoma in its early stages before irreversible damage occurs. As a general rule, have eye exams every two years if you're between the ages of 18 and 60, and every year if you're older than 60. If you have one or more risk factors, you should have eye exams every one to two years until you're 60, and every year after that.
• Treat elevated eye pressure. A large trial at the National Eye Institute found that glaucoma eyedrops could reduce eye pressure by an average of 22 percent. In the same trial, daily use of eyedrops reduced the risk that elevated eye pressure would progress to glaucoma by nearly 50 percent in African-American study participants.
• Control your weight and blood pressure. Recent studies have shown that insulin resistance — which may result from hypertension and obesity — is linked to elevated intraocular pressure
• Wear eye protection. Serious eye injuries can lead to glaucoma. Wear a mask or goggles when you use power tools, play high-speed racket sports on enclosed courts or otherwise risk being hit in the eye.

When to seek Medical Advice

• Don't wait for noticeable eye problems. Primary open-angle glaucoma gives few warning signs or symptoms until permanent damage has already occurred. Regular eye exams are the key to detecting glaucoma early enough for successful preventive treatment.
• It's best to have routine eye checkups every two years if you're between 18-60 years old, and every year if you're older than 60. Because African-Americans have a much higher risk of glaucoma, they should be screened every three to five years from age 20 to 29, every two to four years from age 30 to 40, and every one to two years thereafter. If you have one or more risk factors for glaucoma, talk to your doctor about scheduling more frequent eye exams.
• In addition, be aware that a severe headache or pain in your eye or eyebrow, nausea, blurred vision, or rainbow halos around lights may be the symptoms of an acute angle-closure glaucoma attack. If you experience two or more of these symptoms together, seek immediate care at an emergency room or an eye doctor's (ophthalmologist's) office.
• If you've received a diagnosis of glaucoma, establish a regular schedule of examinations with your doctor to be sure your treatment is maintaining a safe pressure in your eyes.