The above photo is a normal appearing optic nerve. The arrows point to the edge of a crater that we call the “cup”, from which the blood vessels emerge. The margin of the optic nerve is very healthy looking, with good blood supply.
In the bottom picture you can see that there is a lot less healthy-looking margin and a deeper cup. Many people are just made this way with no damage to their eye. But when a patient has glaucoma, the cup always gets deeper and wider like this. So looking at this nerve, I don’t know if the patient has glaucoma or if they are just made that way. I will run a computerized visual field test to rule out any loss of vision from glaucoma.
Glaucoma causes a loss of vision in the periphery, so subtly that you don’t notice it until it’s too late. By the time you notice it it takes only weeks to months to go completely blind. One of the main factors involved in the optic nerve becoming damaged is pressure in the eye. This pressure pinches off blood supply to the optic nerve causing the nerve fibers to die.