My poor duck Penny looked like this when I went to check on the ducks in the yard. I believe it probably happened when my other female was doing her bizarre pseudo-mating stuff - she pulls feathers and sometimes will jump on Penny even on dry land. I applied Terramycin. It seems watery and there's a tiny blood spot along the edge. Sad this happened, I watch them so carefully and usually break them up because I've always been been afraid of an eye injury occurring.