Papilledema is a swollen optic nerve head in the eye. The optic nerve connects the eyeball to the brain. If there is pressure in the brain, it will cause the optic nerve to swell where it enters the eye. The bottom picture below is the normal optic nerve and the top one is a swollen optic nerve head. Note the indistinct margins of the optic nerve on top.
Increased pressure in the brain can occur with or without a space-occupying brain lesion. It is important to rule out any kind of space-occupying lesion such as a brain tumor. This patient had no symptoms. She was just coming in for a routine eye examination. Sometimes patients with papilledema complain of headaches and ringing in the ears.