My horses get those sort of eyes too at this time of the year... when all the grasses come to seed. This is really possible when the paddock she is in has long grass.
I treat the eyes by first buying a fly veil (darker colour) and then get warm water, and then get a tea bag, and wet the tea bag, and then squeeze the tea juice into her eye... I swear it works!!!
Do it 3 times a day, and it should be better by the second day
Goodluck with it :)