Causes
Though glaucoma is a very well known disease and many treatments are available for it, doctors don’t fully understand how it occurs or why it occurs some eyes and not in others.
The cause of open angle glaucoma, in particular, is vexing for doctors. A prevailing belief among doctors and scientists that study glaucoma is that the disease may be caused by an abnormality of the drainage system of the eye, called the trabecular meshwork. This structure is located in the front of the eye where the iris and cornea meet. In open angle glaucoma, though the trabecular meshwork looks normal when it is microscopically examined, doctors believe that some form of intrinsic dysfunction, which is not visible on examination, develops, causing it to become less capable of draining eye fluid, the aqueaous humor. However, the aqueous fluid is constantly being produced by the eye. As such, if the trabecular meshwork drain fails to allow the fluid to leave the eye, the eye pressure can increase, much like an over-inflated basketball.
In angle closure glaucoma,the trabecular meshwork drain may become physically occluded by the iris, abnormal blood vessels or scar tissue, which can also cause dramatic and sometimes rapid rises in the eye pressure.
The increase of eye pressure may be one of the ways in which the optic nerve may become damaged in glaucoma. In fact, many people who suffer from open angle glaucoma have abnormally high eye pressures, suggesting that eye pressure is related to the mechanism of glaucoma damage. However, some eyes can tolerate abnormally high eye pressures without suffering damage at all, whereas others begin to lose vision if chronically high pressures continue over time. Even more perplexing is that some eyes can also suffer glaucomatous damage when the eye pressure is normal, which is called normal tension glaucoma. In short, doctors believe that while eye pressure plays a role in glaucoma, and that lowering the eye pressure is helpful for treating glaucoma, other unknown structural abnormalities in the eye or optic nerve are also at play in the disease.
