Just read this thread. Glad to hear all is well with your horse. Like StarlineStables advised, good to have the needed eye ointments ect...
I deal with Recurrent Uveitis with one of my horses, plus corneal ulcers (due to loss of sight in that particular eye). I have become very good at recognizing the early signs of both. The treatment is the same, except for the ulcers no steroids, so I do not always call my vet. My vet has taught me what and how to do what needs to be done. He also trusts my ability to identify what is going on. If I feel it is necessary, I call him and we discuss what's happening (I'm very good at describing what I see, and have paid close attention to how he diagnoses the condition). I feel we work as a team (I'm the home team:)
Eyes are very sensitive and vulnerable. Something as simple as a small piece of hay chaff can result in a big display, as you have found out. Now you can add this to experience. And now you have a few more items in your medical box for your horse.
Wishing your horse continued good healing.