Glaucoma - Open Angle and Closed Angle

One frequently sees the term angle used in reference to glaucoma. In this context angle refers to the eye s internal drainage mechanism.

As mentioned elsewhere a nutrient-rich clear fluid is constantly being produced in the front part of our eyes. The fluid also known as aqueous circulates nourishing the internal tissues before being drained from the eye. The actual drainage opening for the aqueous is formed by the juncture of the cornea and the colorful iris.

This drainage angle in the eye can be illustrated by visualizing an ocean clam that s right a mollusk. The degree to which a clam is open or closed depends on the angle formed between its upper and lower shells. When the clam is cracked open only a small amount for the sake of illustration think of this opening as a narrow angle . Likewise if the clam is wide open think of it as an open angle .

In the eye the cornea and iris represent the upper and lower clam shells respectively. At the point where these two tissue layers join together an angle is formed....the drainage angle. In most people this tissue angle is wide open (think of the open clam) and the aqueous fluid has the opportunity to flow out of the drain unimpeded. However in a smaller percentage of the population the drainage angle is very narrow or nearly closed so the drainage of the aqueous becomes problematic. In this case the eye pressure can rise.

Nearly everyone is born with a wide open drainage angle but the angle tends to become shallower with age. Also the drainage angle is characteristically smaller in individuals who are far-sighted. The growth of a cataract (refer reader to Cataracts and Eggs link) will cause the angle to become narrower with time. The removal of a cataract tends to restore the angle to its wide-open status.

Open-angle glaucoma is the most common form of the disease. One might ask: If the drain is wide open why is there a problem? This would be an excellent question. For reasons not completely understood even though the drainage angle is wide open in these open-angle glaucoma patients the aqueous drainage is not effectively controlled and the eye pressure goes up.

In narrow-angle glaucoma the drainage opening is typically very small (visualize the clam shell being open only a tiny amount) thereby making it difficult for the aqueous to drain from the eye.

It is even possible for the drainage angle to close completely permitting very little if any aqueous to drain from the eye. When this happens the eye pressure can skyrocket to dangerously high levels. This is considered an emergency crisis and requires immediate intervention. Fortunately this angle- closure attack is relatively rare. But when it does happen the individual can experience a great deal of pain and could suffer permanent vision loss if not attended to immediately.

What can be done?

Your doctor will assess the status of your drainage angle. If your eye pressure is too high and you have an open angle it s likely that the treatment will focus only on lowering the pressure to a safer level. If your drainage angle is dangerously narrow your doctor may suggest that a precautionary laser procedure be performed in order to facilitate the drainage of aqueous and prevent the pressure from becoming too high.