This directs the foam into those areas which are more difficult to seal. At the inner corner of the eye the frame pushes the sponge against the side of the nose, and into the depression which often occurs across the top of the bridge of the nose. The frame pushes foam into the depression between the nose and the cheekbone. It also allows for the cheekbone by curving in to more closely match and apply less pressure over this area. At the outer corner of the eye, it pushes almost directly back to fill the depression near the outer canthus of the eye.
Some swimmers have no marks at any time.
The reduced pressure of the frame against the face is also important because it reduces pressure of the frame over sinuses and nerves. The size of the goggle is only important in how well it covers the eye, and how much you want to trade a wide field of vision for low drag. The external shape isn't as much about how the goggle seals as it is about how little it will slow you down in the water. Generally speaking, drag from a goggle is directly related to how far it stands out from the face. In other words, how much area there is to resist the water.