On the way to the barn, the vet called me back.
Here is the surprising thing: the vet thinks that Isis might not have had another EPM episode/relapse. (Granted, she can’t say for sure since she hasn’t seen Isis.) She said that she thinks Isis might have had a head trauma. Blindness in horses can be caused by head trauma, and it usually resolves quickly. In June 2009, the blindness caused by Isis’ EPM took about 36 hours to resolve when she was in the hospital.
There is still a chance that this could have been an EPM episode, possibly a relapse. Dr Stinson is coming out on Tuesday at 10:30 to evaluate Isis for head trauma, signs of EPM (blood test), and also to see if it might be safe to take Isis to clinics or shows (assuming this is not an EPM episode).
I’ll post more updates as I have them.