Look inside the ear, see if there's pus in it.
Look inside the beak for any lesions, white or yellow pasty material.
Any bad odors?
Yes, you will want to still treat the eye.
Depending on what's causing the infection, Tylan may still be the correct antibiotic to give.
Have you ever had respiratory illness within your flock?
It looks like conjunctivitis. Could be from an irritant, but sometimes sunken eyes like that can indicate Mycoplasma as well.
I'd give general care to see if there's improvement. Flush the eye with saline, then apply Terramcyin eye...