Acanthamoeba spp.

Acanthamoeba species in corneal scraping (Papanicolaou stain, oil immersion). Two cysts of this ameba show the characteristic double wall—a wrinkled, fibrous outer wall (ectocyst), and an inner wall (endocyst) that may be smooth and appear polygonal, hexagonal, spherical, or star shaped. The nuclei of the cyst are not visible.