What Causes Glaucoma?
In most cases, glaucomatous optic nerve damage occurs from high eye pressure. For some people, fluid can’t drain properly because of a faulty drainage system. Drainage that once worked well may gradually slow down as you get older. Similar to a sink that becomes clogged and backs up with water, when the aqueous humor in the eye is unable to drain adequately and there is no place for the excess fluid to go, pressure inside the eye builds up.
1. Other factors besides intraocular pressure appear to contribute to glaucoma. Some people with normal pressure may experience vision loss from glaucoma, and many people with high IOP (ocular hypertension) do not develop glaucoma. However, the higher the IOP, the more likely optic nerve damage will occur. Some normal tension glaucoma may be related to problems with blood flow in the eye. Doctors continue to study eye pressure and other possible causes of glaucoma.
2. Nerve damage can usually be slowed down or stopped by lowering the eye pressure. The goal of glaucoma treatment is to lower the eye pressure with medicines, lasers, or surgery. Although vision loss from glaucoma cannot be restored, treatment can typically slow down or prevent further vision loss.
What is Eye Pressure?
Aqueous humor (the nourishing fluid within the front of the eye) leaves the eye through a tiny drain called the trabecular meshwork (Figure 2).
The trabecular meshwork is located on the side of the eye, just in front of the iris (the part which gives an eye color). Since the fluid is made just behind the iris, it must pass between the iris and lens before leaving through the trabecular meshwork (Figure 3a).
The balance between how much fluid is made, and how much leaves the eye, determines the pressure within the eye. All eyes have measurable pressure. However, when the amount of aqueous humor draining from the eye is reduced, the pressure within the eye can increase. This high pressure often leads to glaucoma.
