Well Charlie and I just got back from the vet.
Yesterday morning he woke me up sounding like he needed to go potty. I got up took him outside, then went back in to put on my coffee (reverse order from our normal schedule). In less than 5 minutes I went out and he had his right eye completely closed. Don't know...sigh. Poked himself with the stick he chews on, bug bite, cornered a squirrel??? We'll never know.
Anyway, I flushed his eye with sterile saline solution. After about two hours, he had his eye half-way open but still squinting. By mid-afternoon he was looking better still and by bedtime he looked almost fully alert. I was flushing his eye every couple hours, and aside from the squinting, he was not tearing or having any other discharge. This morning he looked fully back to normal.
Took him for a walk this afternoon, and he started squinting again, so off to the vet we went. They put a dye in his eye to check for scratches. Could not find anything in his eye or any sign of a scratch. The vet looked under his inner eye lid with some little scary looking tool and didn't see anything.
He ended up diagnosing him with a "marginal entropy". My understanding is that whatever irritated Charlie's eye caused a slight swelling/squinting that rolled his eyelid in so the eyelashes were touching the eye and keeping him from improving after whatever irritated the eye was gone.
I'm a little confused whether this is going to be an ongoing problem requiring surgery, or just something to watch for if he develops an allergy or gets an irritant in his eye. I asked, and think my answer was "yes...or maybe"...not very clear.
I can't imagine he would be fine all his life so far, then develop a permanent entropion in five minutes while I made coffee. Anyway, I guess we'll see. Right now I'm putting antibiotic eye drops in 3x a day for the next week.