What is glaucoma?

Glaucoma is a condition that results in optic nerve damage and peripheral vision loss in a characteristic pattern. The only modifiable factor that we know that can modify the disease course is lowering the intraocular pressure. Even though glaucoma is one of the most common causes for blindness, our knowledge of the cause for the optic nerve findings are limited as stated in the previous definition. Typically glaucoma is associated with an elevated intraocular pressure, but not always. In susceptible individuals this elevated pressure results in damage to the optic nerve that usually starts with peripheral vision loss and can extend to central vision loss. The amount of nerve tissue that can be damaged before the patient is able to notice their vision is decreased can be substantial. However, once the vision is noticed to be decreased, it is usually much more difficult to stop the progression. This is why it is extremely important to identify glaucoma at an early stage. Glaucoma may be due to decreased blood flow to the optic nerve head or due to deformation in the anatomy of the optic nerve at the lamina cribrosa, but we do not know all the details at this point in time. In your eye, fluid is produced at the ciliary body which is behind the colored part of the eye called the iris. This fluid circulates in front of the pupil and out through the drain called the trabecular meshwork. The cause for the high pressure is usually from decreased outflow in the trabecular meshwork. The most common cause of this is primary open angle glaucoma or POAG. This is the medical community's way of saying we do not know why it occurs. There are genetic and behavioral factors that contribute and we have found some genes associated with POAG. Other causes for "clogging" up the drainage include pigmentary dispersion glaucoma and pseudoexfoliation glaucoma. Pigmentary dispersion results from the iris (the blue or brown part of the eye that one sees) rubbing against the fibers that hold the lens of the eye up, and that pigment collects in the drainage. Pseudoexfoliation glaucoma results from a substance being produced from the body that also can result in loosening of the fibers that support the lens, and also collects in the drainage system. There is a type of glaucoma called angle closure glaucoma that results from the space for fluid to drain out the trabecular meshwork being decreased. This can be caused by adhesions due to inflammation or anatomy, or it can occur immediately from an entity called pupillary block. There are many other types of glaucoma, but this is an overall sampling. As you can see, glaucoma is not one entity, but a number of different entities that have a similar outcome. If you need an appointment, or eye doctor, please call 512-686-1224 to schedule an exam.