We had one mare , that eventually did go blind, who was improved for several years with her flymask. They also help keep dust and debri out of the eyes. We ride with them on. I hope this is helpful info for you. I'll have to look into it some more.
Horses are unpredictable.
If you are not experienced, handle horses under the supervision of a qualified instructor. This forum is not intended to be an instructional guide, and any one who uses it for this purpose, does so at their own risk. All rights reserved. Reproduction of this site in whole or part without permission is prohibited.