It looks like conjunctivitis. Sometimes that is a symptom of a respiratory disease, but can be a result of a foreign body or sand in the eye, a peck, or ammonia fumes feom poop. Do you see any bubbles in the eye? I would try some Terramycin eye ointment from the feed store, apply a dab 2-3 times a day. Antibiotic or steroid eye drops may be prescribed by a vet.
Update:
The swelling of the eye has gone down and it’s almost perfectly open and clear again. That topical antibiotic seems to have done the trick! Thanks for the support!