Anatomically Narrow Angles

Anatomically Narrow Angles

The Angle is referred to the area where the iris is attached to the wall of the eye. This is also referred to as the gonio angle. The gonio angle is therefore 360 degrees around the eye. The angle is where the trabecular meshwork resides and allows for drainage of fluid from inside of eye structures. The fluid inside of the eyeball is replenished on a regular basis (2-3 microliters per minute) and therefore all the fluid is replaced every 2 hours. If the drain is blocked, fluid builds up and the pressure of the eye can rise rapidly. In fact, when angle closure glaucoma attach occurs, the pressure can get as high as 50 mmHg (normally in range of teens).

In the normal eye the angles are open about 45 degrees with back side of iris lying flat again the lens. Look at the image below as an example of a normal anterior segment. The "angle" is the angle between the area dotted green trabecular meshwork and the front side of the iris.

Visante Image of the anterior segment of the eye.  Dr. Ash has outlined the major structures

In case of Narrow angles that area becomes much narrower. It is very important to remember that there are many factors that influence this structure such as drugs and light. As iris is a dynamic structure, with light as the pupil comes smaller, the angle also opens up. See below the change in angle size in a patient with anatomically narrow angles.

Visante Image of the angle showing the changes caused in the opening due to light

It can be noted in the image above with plain view and with angle tools below that at angle size of 2.20 mm the pupil is open to 21.7 degrees, but in the natural state of pupil at 3.85 mm, the angle virtually closed at 2.9 degrees.

Pupil Size direcly affects the opening of the angles as noted in this Visante image by Dr. Ash

Page last edited 07/04/11