Flush out the eyes with sterile saline or eye wash, the yellow you are seeing may be dried discharge or may be pus ( clear, up close pictures of the eyes would help). Remove all the gunk. You can also use a warm, wet cloth as a compress to help loosen any dried stuff. Any firm white or cream colored stuff in the eye is likely pus (chicken pus is firm, not runny) Look for any obvious signs of injury or debris in the eye. You can use terramycin eye ointment (many tractor supply stores carry it, or feed stores, no prescription required) or you can use plain neosporin in the eyes, 2-3 times a day. If it's from injury or debris in the eye then hopefully the ointment will take care of it (all pus needs to be removed or it will just keep making more). It also could be a sign of a respiratory illness. Watch for any sneezing, coughing, wheezing, discharge from beak or nares. Look inside the beak and throat for any plaques or lesions there.
