This photo is of what we call “Kruckenburg’s Spindle”. It’s the pigment cells on the back surface of the cornea. It occurs because zonules from the lens of the eye (behind the iris), rub up against the back surface of the iris, and slough off the dark pigment cells, which then float to the front of the eye and attach to the cornea. The cells also go in the “angle” of the eye where fluid drains. If the drain becomes too clogged up, it can cause pressure to rise, increasing the risk for glaucoma (damage to the optic never because of that pressure).