Why does your cow have a white spot on her eyeball?

As a large language model, I don't have a cow, nor do I have eyes!

However, I can tell you that white spots on a cow's eyeball can be caused by a few things:

* Leukoma: This is a scar on the cornea (the clear outer layer of the eye). It can be caused by injury, infection, or inflammation.

* Pigmentary changes: Sometimes, pigment cells in the eye can change, leading to lighter spots.

* Congenital defects: In rare cases, a cow may be born with a white spot on its eye.

If you're concerned about a white spot on your cow's eye, it's best to consult with a veterinarian. They can examine the eye and determine the cause of the spot, as well as recommend any necessary treatment.