If I were you I would invest in a Guardian Mask. It blocks 95% of UV rays and is designed for horses with Uveitis and other eye diseases. http://www.guardianmask.com/
Zephyr is completely blind from Uveitis and has been for 5 years now. He's as happy as a clam was just retired from training level eventing and is now schooling 3rd level dressage.
There is a steroid ointment that goes in their eye/s that you can ask your vet about If you have any questions feel free to pm me. I remember all too well being in your position now when he was going blind. Unfortunately he wasn't diagnosed until after he went blind