Glaucoma a Hushed Bandit of Sight

Glaucoma is a Leading cause of irreversible blindness in the world Causes no symptoms early in its course Can affect people of all ages, even newboms.

What is Glaucoma?
Glaucoma is a group of eye diseases that damage the major nerve of vision, called Optic Nerve. Light generated nerve impulses from the retina are received by optic nerve.These impulses are transmitted to the brain where we recognize them as Vision. Glaucoma is characterized by a particular pattern of progressive damage to the optic nerve that generally starts with a subtle loss ofside vision (peripheral vision). If not diagnosed and treated, it can progress to loss of central vision leading to blindness.

How common is Glaucoma?
Glaucoma is the second leading cause of irreversible blindness in th world. In India alone, at least 12 million people have glaucoma. Mo than 90% of glaucoma cases may not even know that they have theeven know that they have the disease. Since it is a silent thief of sight, it initially causes no symptoms, and hence the subsequent loss of side vision is usually not recognized.

What causes Glaucoma?
Glaucoma is mostly, but not always,associated with elevated pressure in the eye (intraocular pressure). Generally, it is this pressure that damages the optic nerve. In some cases, glaucoma may also occur in presence of normal eye pressure, which is believed to be caused by poor regulation of blood flow to the optic nerve.

What is so important about intraocular pressure?
Eye is firm and round. Its tone and shape are maintained by a pressure within the eye (the intraocular pressure), which normally ranges between 8 mm (millimeters) and 22 mm of mercury. When the pressure is too low, the eye becomes softer, while an elevated pressure causes it to become harder. Optic nerve is the most susceptible part of the eye to high pressure, as the delicate fibers in this nerve are easily damaged either by direct pressure on the nerve or decreased blood flow to the nerve.

The front part of the eye is filled with a clear fluid called the aqueous humor, which provides nourishment. It should not be confused with tears, which are produced by the lacrimal glands. Aqueous humor is constantly produced and surrounds the eye lens. It then flows through the pupil (small, round, black-appearing opening in the center of the iris) and leaves the eye through tiny drainage channels (Trabecular meshwork). Figure shows the drainage angle between cornea and iris. The yellow Flow of the Aqueous Humor arrow shows the flow of the aqueous humor which must be balanced to maintain the optimum eye pressure.

In most of the people, drainage angles are wide open, but in some individuals, they can be narrow. For example, the usual angle is about 45 degrees, whereas a narrow angle is about 25 degrees or less. After exiting through the trabecular meshwork, the aqueous humor then drains into tiny blood vessels (capillaries) into the main bloodstream.

This process of producing and removing the fluid from the eye is similar to that of a sink with the tap always turned on, producing and draining the water. If the sink's drain becomes clogged, the water may overflow. If this sink were a closed system, as is the eye, and unable to overflow, the pressure within the sink would rise. Likewise, if the eye's trabecular meshwork becomes clogged, the intraocular pressure may become elevated. Also, if too much fluid is being produced within the eye, the intraocular pressure may become too high, causing damage to the optic-nerve leading to glaucoma.

Who is most at risk for glaucoma?
People with eye injury, myopia, family history of glaucoma, conditions like blood sugar, high blood pressure, thyroid, or are on long term corticosteroids are at great risk.

How can glaucoma attacks be prevented?
While glaucoma is not reversible, if it is recognized in the early stages, further blindness or significant vision loss can be prevented. Medications to reduce the elevated pressure, laser treatments or surgery are also available. Moderate exercise such as walking or jogging three or more times a week and routine eye check up can lower its effect.