Glaucoma is a progressive optic neuropathy causing peripheral vision loss not attributable to other causes.
I hope that is clear.
The optic nerve is the cable that runs from the back of the eye to the brain. It carries the information of what the retina has seen to the brain to be perceived as images.
In glaucoma, the fibers which make up the optic nerve can degenerate over time. It is believed that the most common risk factor for developing glaucoma is high pressure in the eye.
There are several other types of glaucoma listed below, but the most common is Open Angle Glaucoma.
To diagnose and treat glaucoma, we often do several tests. The one which is done every time is measuring the intraocular pressure. This is done with a yellow drop and the blue light. In the past, some people screened for high IOP with an air puff test. We do not do that.
Other tests include a peripheral vision test. You must stare straight ahead and press a button when a small light flashes in your side vision. Most people do not like this test very much.
We also will do an Optic Nerve OCT which measures the shape of the optic nerve and retina. I use a high resolution OCT made by Optovue.
Other testing can include gonioscopy, or checking to make sure you have open angle glaucoma and not any other reason for glaucoma. We also check corneal thickness. See the ocular hypertension page.