The eye has bubbles in it and some crusty drainage. Sometimes you may see that with mycoplasma gallisepticum (MG) a respiratory disease. Have you seen any sneezing, nasal drainage, sleepiness, or noisy breathing? I would rinse the eye with saline or water, and apply Terramycin eye ointment twice a day. If he could have been pecked in the eye or gotten something in there, it may have caused some infection. Have a look inside the eye for anything unusual.