A number of. Parasites including loa loa, a filiarial worm that can wriggle across the white of the eye.
Many. There are number of parasites that have been found in eyes. Fortunately, this is a rare occurence in the U.S. A few of the more common ones are toxocara canis, the dog roundworm, histoplasma, a fungus endemic in the ohio river valley and toxocara, a protozoan, passed to fetuses from mothers who handle cats during pregnancy.