Glaucoma
Glaucoma is a group of eye diseases where vision is lost due to damage to the optic nerve. Glaucoma affects many millions of people worldwide. Glaucoma is the second-leading cause of blindness worldwide after cataracts. In the United States about 7% of the population 65 years and older is affected. Peripheral vision may begin to decrease followed by central vision resulting in blindness if not treated. The most common type is open-angle glaucoma with less common types including closed-angle glaucoma and normal-tension glaucoma. In the past the various forms of glaucoma were thought to be solely due to mechanical problems: either increased pressure on the optic nerve from some form of trauma, or decreased blood flow (ischemia) to the optic nerve. However, it has long been apparent that increased pressure throughout the eye only damages certain cells in the eye and that the drugs used to decrease the pressure, though sight-saving, do not completely stop the progressive visual loss. Current research offers an explanation for why this is so.
Glaucoma is increasingly thought of as a neurodegenerative disease rather than a simple mechanical problem. The same neurochemical events leading to neuronal cell death in ischemic optic neuropathy also occurs in glaucoma. There is still much to be learned about how glaucoma causes visual loss, but enough is already known for researchers in many laboratories to be on the hunt for ways to protect nerve cells from damage in glaucoma. Results of this important research may impact treatments for other optic nerve and neurodegenerative diseases.