I do not keep any systemic antibiotics, and don't plan to. They expire, can be obtained if needed, and are too often given incorrectly -- when they shouldn't be, or the wrong one.
You can buy antibiotic ophthalmic ointment in a feed store off the shelf. You can also use plain Neosporin ointment in the eye.
Amprolium is not an antibiotic and is indeed a good thing to have on hand if your flock gets sick with cocci, as it needs quick treatment. On the other hand, I've had several flocks and have never seen a case of cocci. Also, broody raised chicks are evidently less likely to get sick with cocci, probably because they get some additional immunity from eating some of mama's poop.
I keep BluKote and a pyrethrin/permethrin spray as a lice/mite preventative. I keep Neosporin, peroxide and Betadine for myself, and have used them on the chickens a few times. Simple enough to avoid cross contamination. I also have some Valbazen and will be worming my bunch soon.