Optic disc swelling

Top: Fully developed optic disc swelling, in this case papilledema. Note the absence of distinct disc margins, obstruction of blood vessels as they cross the disc margin, hemorrhages, and cotton wool spots. The blood vessels change course abruptly as they approach the disc because they are running up and over the elevated disc substance. Bottom: Mild optic disc swelling. Note the concentric lines (Paton's lines) in the retina next to the disc (arrow). This occurs because the swollen disc pushes the retina aside.