Well. That's certainly a wealth of information to go on.
If the hen is walking and drinking and otherwise behaving normally while keeping both eyes shut, it could mean she has a painful eye issue. Bacterial infection or pink eye can cause pain in the eyes. Flush with eye wash or a saline solution. Then place an ophthalmic antibiotic ointment in each eye twice a day.
If the hen is mostly lethargic and standing around doing nothing with eyes closed, she's got something far more serious going on.