Glaucoma is relatively easy for the layperson to understand because medical science really dose not understand the disease either and has thereby simplified matters.  Physicians view the disease in terms of eyes with too much pressure but there is a far more complex nature to the disease.  So the condition can be looked at as an eyeball with too much internal pressure to allow for the health of the optic nerve..  As a result, the nerve becomes damaged and vision is lost.

The eyeball is a closed system with fluid (aqueous humor) continually circulating in and out via a highly regulated structure (trabecular meshwork).  If the production of fluid remains constant and there is a problem with the outflow, the pressure must rise.  The optic nerve connects the eyeball and the brain and inserts itself into the back of the eye.  This nerve is very sensitive to pressure changes and if the pressure remains too high, the nerve becomes damaged.  When damage occurs to the nerve, vision is lost in a characteristic pattern; the periphery of the vision is lost long before the center of vision is effected.  If untreated, the central vision is ultimately lost and blindness ensues.

The most common type of glaucoma is open angle and a less common form is narrow angle or closed angle.  The “angle” refers to the region on the inside of the eye where the clear cornea meets the iris (colored part of the eye).  It is in this angle that the fluid passes out of the eye.  In narrow angle glaucoma the iris bulges too far forward and touches the cornea thus obstructing the flow to the angle.  When this occurs, the pressure in the eye raises very quickly causing severe pain and loss of vision.  It becomes a medical emergency.  This relatively rare situation most often occurs without warning in people who are anatomically predisposed, i.e., they have small eyeballs with crowding of the angle.  Sometimes cataract formation in the presence of a small eyeball can precipitate the angle closure.

Open angle  glaucoma is far more common and occurs as a result of a defect in the trabecular meshwork which is the structure in the angle through which the fluid must pass on its way out of the eye.  So here the angle is open but the filtration mechanism does not function properly.  The net result is that the pressure raises above normal but usually in a much more gradual rate.  Since the pressure raise is gradual there is no pain but damage to the optic nerve nevertheless develops.  Since the resulting visual loss occurs in the periphery, most people don’t realize that there is a problem.  I saw an elderly gentleman in the office who had undiagnosed advanced glaucoma.  He had attempted to drive his car between two side-by-side trucks on a four lane highway since he only saw one of them.  This is an example of how bad the disease can become.

If left untreated the vision loss extends to the center of vision.  This is one of the reasons for a routine ophthalmic examination on a periodic basis.

Treatment options will be discussed in a future blog.