Friday, December 05, 2008

Learn more about Glaucoma

What is Glaucoma? What are the common types of Glaucoma? What are the risk factors, causes of Glaucoma? What are the treatment options for Glaucoma? How do i use eyedrops medicines?

First and foremost, lets take a look at the structure of our eyes.

The Sclera is the white part of the eye while the cornea is the clear membrane in the front of the eye over the black circle (pupil) and colored ring (iris). Light passes through the pupil into the eye. The pupil becomes small (constricts) in bright light and larger in dim light.

The lens of the eye is a small and clear disc. The lens can become cloudy, for example, in Cataract. Retina contains sensory cells, i.e. cones (differentiate colors) and rods (differentiate shades of grey), where they function to absorb light.

There are millions of optic nerves in total and they function to connect the retina to the brain, hence they are essential for our vision. Glaucoma is basically linked to damaged optic nerves.

What is Glaucoma?

Glaucoma is a group of diseases that can damage the optic nerves of the eyes. It is known as 青光眼(qing guang yan) in mandarin. As time goes by, if left untreated, it will eventually leads to vision field lost and subsequently progress to blindness. Glaucoma might or might not be related to raised intraocular pressure (IOP) (>22mm Hg). Increased IOP is an indicator for Glaucoma only.

What are the risk factors, causes of Glaucoma?

Everybody is at risk of developing Glaucome but it is more common in people falling in these categories :

- African Americans over age 40.
- Everyone over age 60, especially Mexican Americans.
- People with a family history of glaucoma.

In a healthy person, clear fluid flows in and out to nourish the surrounding tissues. However, sometimes the fluid passes too slowly and results in increased IOP when the fluid builds up. It is said that the level of pressure your optic nerve can tolerate without being damaged will determine whether you will develop glaucoma. One thing to note is that Glaucoma occurs when your optic nerves are unable to tolerate the increased IOP and thus leading to damage.

What are the common types of Glaucoma?

The most common one is Primary open-angle Glaucoma. Other types of Glaucoma include angle-closure Glaucoma, low tension/normal tension Glaucoma and Secondary Glaucomas.

What are the treatment options for Glaucoma?

It is very important to control the disease to prevent losing vision.

A person with Glaucoma loses peripheral (side) vision initially and may lose straight-ahead vision slowly until no vision remains if left untreated. The pictures below indicate person with glaucoma unable to see side clearly (LEFT) and a healty person is able to see the full view clearly (RIGHT).

Taken from National Eye Institute entitled facts about Glaucoma.

The most basic treatments for Glaucoma is by medicines. Other options incldue laser trabeculoplasty, conventional surgery, or a combination therapy. It is important to understand that treatments only help to save the remaining vision but not improve the sight already lost from Glaucoma.

There are a few different classes of medicines used to treat Glaucoma, where all the drugs worked by lowering the IOP.

- Beta blockers (eg. Timolol) --> reduces the rate of production of aquoes humor and thus reduces the IOP.
- Prostaglandin analogues (eg. Bimatoprost) --> increases uveoscleral outflow of aquoes humor.
- Slective Alpha-2 adrenergic agonists (ef. Brimonidine) --> dual mechanisms action i.e. reduces aquoes humor production and increases uveoscleral outflow to reduce IOP.
- Carbonic anhydrase inhibitors (eg. Dorzolamide) --> reduces the secretion of aquoes humor and thus reduces the IOP.

p/s : Eyes medicines usually available in eyedrops. These eyes medicines are not cheap at all, ranges from rm50 to rm 80 per bottle.

Simple instructions on using eyedrops medicines :

  • First, wash your hands.
  • Hold the bottle upside down.
  • Tilt your head back.
  • Hold the bottle in one hand and place it as close as possible to the eye.
  • With the other hand, pull down your lower eyelid. This forms a pocket.
  • Place the prescribed number of drops into the lower eyelid pocket. If you are using more than one eyedrop, be sure to wait at least five minutes before applying the second eyedrop.
  • Close your eye OR press the lower lid lightly with your finger for at least one minute. Either of these steps keeps the drops in the eye and helps prevent the drops from draining into the tear duct, which can increase your risk of side effects


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