Have you taken any pictures of his eyes? Do you think it is from a respiratory disease, such as MG or coryza? Is there a bad odor? Bubbles or foam, or pus in the eyes can be a sign of MG, and that with a bad odor can be coryza. They cause conjunctivitis and sinus infection. Both are contagious to the whole flock, and those remain in the flock for the life of the chickens. If there is pus in the sinus, the eyelids may need to be pressed slightly to express the pus, or the swelling may not go down. If you can get Tylan or Tylosin, that can treat MG symptoms. Sulfadimethoxine is more for coryza.