The strongest ocular specular reflection occurs at the anterior tear film, where the interface index difference is largest. Weaker reflections are generated at optical interfaces internal to the eye. Purkinje images . Optics omnidirectional optical scatter from rough surfaces or volumes containing internal scattering centers. Diffuse reflection is negligible from liquids, like the tear film and aqueous humor, but is significant from tissues, like the cornea, iris, and crystalline lens.
All reflective techniques suffer from perspective ambiguity .