The eyeballs of humans and the eyeballs of cows have a similar structure overall. Both have the sclera, which is the white part of the eyeball, cornea or the clear structure over the iris and pupil, lens, vitreous fluid, retina and choroid. The choroid is the layer of the eyeball that is between the retina and the sclera. However, despite the many similarities, there are differences between a cow eye and a human eye.