Hi,
I'm sorry that your horse is having trouble with its eye. I consider eyes to be "urgent" matters. Things can start small, and even 1-2 days delay in treatment can make something that would have been easily fixed, a mess. I would most definitely make a call to your vet in the morning. She may have something stuck beneath the eyelid or the start of an infection. Either way, it needs to be examined.
Let me know how it works out. If you need further information, let me know.
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