Glaucoma

Glaucoma is one of the main causes of blindness, especially as we grow older.

To most of us, Glaucoma has something to do with the pressure inside the eye. In fact, glaucoma is really a disease of the optic nerve.

In this disease, the pressure inside the eyeball, or the intraocular pressure exceeds the ability of the affected eye to tolerate it. This damages the optic nerve, gradually leading to total blindness. The optic nerve is like an electric cable containing hundreds of wires. Each 'wire' or nerve fibre caries a message to the brain. These messages join together to provide vision. Glaucoma can damage nerve fibres, causing blind spots to develop.

Unfortunately, symptoms appear only after damage has already happened. Early detection and treatment are the key to preventing optic nerve damage and blindness from glaucoma.

Causes and Types

A clear liquid called aqueous humor continuously flows within the eye. This liquid is not part of the tears on the outer surface of the eye. The production and drainage of this fluid can be compared to a sink with the faucet turned on all the time. If the 'drainpipe' gets clogged, water collects in the sink and pressure builds up. If the drainage portion of the eye, called the drainage angle, is blocked, the fluid pressure within the innner eye may increase and that can damage the optic nerves.

There are four kinds of glaucoma

1. Chronic Open Angle Glaucoma
The outflow of the aqueous is impaired because the pores of the trabecular meshwork, from where the fluid usually drains out of the eye, are blocked.

2. Closed Angle Glaucoma
The outflow of aqueous is impaired because of a crowding of the iris tissue at its outer edge, which affects internal circulation.

3. Secondary Glaucoma
Eye injuries, inflammation of the iris, growth of new blood vessels over the angle after certain eye surgeries, and intraocular tumors, increase intraocular pressure and can lead to secondary glaucoma.

4. Congenital Glaucoma
Congenital glaucoma occurs when the drainage angle is abnormal at birth.

Signs and Symptoms:

• Mild and frequent headaches. This may be the only symptom in case of open angle glaucoma
• Severe headaches suggest attacks of closed angle glaucoma.
• Redness and watering of the eye.
• Frequent change in eye glasses
• Blind spots in the field of vision, which might even progress to missing areas. In such a case, the affected person will bump into objects that are on his sides.
• Rainbow coloured haloes while looking at light, especially in the evening.
• Loss of sight, if the disease has progressed very far.
• In congenital glaucoma, the child's eye may show tearing, enlargement of the eyeball or corneal haziness.

Risk Factors:

• Advancing Age
• Near-sightedness
• Family history of glaucoma or diabetes
• Past injuries to the eye
• History of severe anemia or shock
• If your risk of developing glaucoma is higher than normal but there is no optic nerve damage, you will be monitored periodically as a glaucoma suspect.

Diagnosis and Treatment:

• Special checks are performed by the opthalmologist to diagnose glaucoma. Some of these are gonioscopy for checking the drainage angle, tonometry for checking intraocular pressure, perimetry for checking the visual fields, and opthalmoscopy for checking the optic nerve.
• If the tests suggest that the intraocular pressure is higher than normal, the patient is put through a series of investigative procedures.
• People with any kind of glaucoma need regular examinations throughout their lives.

Medicines:

• Drugs in the form of drops and tablets are the mainstay of glaucoma treatment. Tablets are used to control the intraocular pressure temporarily, while the drops have to be used lifelong.
• Usually, eye drops are taken several times a day, sometimes in combination with pills. These act to decrease the eye pressure either by slowing the production of aqueous fluid within the eye or by improving the flow leaving the drainage angle.
• These medicines sometimes also have side effects like reddening of the eye, headaches, blurring of vision, changes in pulse, heartbeat and breathing.

Laser Surgery:

• These days, lasers are also used in the treatment, both for open angle and closed angle glaucoma. In open angle glaucoma, laser may succeed in reducing the dependence on eye drops to a certain extent and for a limited duration of time. In this case, the drain is treated by performing trabeculoplasty.
• In closed angle glaucoma, a hole is made in the iris to restore the flow of aqueous fluid to the drainage angle.

Operative Surgery:

• If a person fails to respond to the above treatment, corrective surgery is performed on his eyes.
• Only in selected cases and advanced forms of glaucoma, a mechanical drainage device is fitted in the eye. This ensures efficient clearing of the aqueous and prevents pressure on the optic nerves.
• Sight loss due to glaucoma cannot be regained. All treatment strategies aim to slowing down further loss.

Preventive Measures

• If there is a history of glaucoma or diabetes in your family, a comprehensive annual checkup is recommended, especially if you are over 40 years of age.
• If you have had a serious eye injury in the past, or have been taking steroids for a long time, regular checkups are a must.
• Once glaucoma is diagnosed, you will need to stay in constant touch with your opthalmologist.