Types of Glaucoma
The Science of Glaucoma and the Types of Glaucoma,
Aqueous Fluid & Intraocular Pressure (IOP)
Aqueous fluid is a clear and watery ultra-filtrate of blood that fills the anterior and posterior chambers of the eye. Flowing more at night than in the day, it is a source of nourishment for the eyes and plays a part in waste removal. The eye forms and reabsorbs aqueous fluid continuously. The regulation of intraocular pressure (IOP) is in part a result of the flow of aqueous fluid. IOP can be determined by comparing the inflow versus the outflow of aqueous fluid in the anterior segment (the chamber on the front of the eye covered by the cornea) IOP remains constant if the outflow is equal to the inflow. If outflow is less than flow, the IOP rises.
Most people with glaucoma suffer from one of two major types of the disease, “open angle” and “closed angle” glaucoma.
What is the Angle?
To better understand these two types of glaucoma we first have to explore why the term “angle” is used to describe them. The anterior chamber is the fluid-filled space inside the eye between the iris and the cornea's innermost surface, the endothelium. Aqueous fluid fills the anterior chamber. In differentiating between open angle and closed angle glaucoma experts use the iris, the corneal endothelium and the trabecular meshwork as points of reference. The anterior chamber angle is often referred to as “the angle”. The base of the angle is the iris. The apex of the angle is the trabecular meshwork. The top of the angle is the corneal endothelium. If a miniature protractor could be placed on the base of the angle (the iris) to determine the width of the anterior chamber angle degrees a 45 degree angle would be considered wide (or “Open”) and a ten degree angle would be considered, narrowed or “Closed”.
- Chronic open-angle glaucoma:
This is the most common type of glaucoma. The drainage angle, where the fluids in the eye drain, is open, but working less efficiently. The inability to drain causes pressure within the eye to rise, which results in a gradual loss of peripheral vision. This can be likened to an air filter, which gathers dust over time & eventually becomes too laden with dust to work properly.
- Angle-closure glaucoma:
This type of glaucoma occurs when the drainage angle is completely blocked, often by the iris. This prevents any fluid to drain from the eye & causes the pressure within the eye to suddenly rise. Common symptoms that are caused by this extreme rise in pressure include blurred vision, headaches, severe eye pain as well as the appearance of halos around lights.
- Chronic angle-closure glaucoma:
This is painless and more gradual closing of the drainage angle, which occurs most frequently in people of African or Asian descent.
- Secondary Glaucoma:
This type of glaucoma progresses very much like chronic open-angle glaucoma. It occurs when scar tissue blocks the drainage angle. The first symptom is loss of peripheral-vision.
- Congenital Glaucoma:
This is a birth defect, which affects the drainage angle. To prevent blindness, this condition must be treated shortly after birth. Symptoms include enlarged eyes, a cloudy cornea, light sensitivity and excessive tearing.
Page Content Includes: The science of glaucoma, types of glaucoma, chronic open-angle glaucoma, congenital glaucoma, secondary glaucoma, chronic angle-closure glaucoma, Angle-closure glaucoma, what is the glaucoma angle?