Was there or is there any sign of watering from the eye or does it look like the eyelashes have rolled in? This normally happens with entropian where the bottom lid has turned in. If you carefully pull it down you may see signs of some lashes rubbing the eye.
It can be treated with antibiotic ointment, if eyelid still rubbing then vet may need to inject some antibiotic into it to keep it out. The redness is the eye trying to heal.
I have had trouble with this but my vet is very good and treated it easily with no distress to lamb, Now perfect.