A system of regular ridges instead of nipples on a compound eye that has to operate near the diffraction limit.

A system of regular, radial ridges, spaced approx. 250 nm apart, is reported from the outer corneal surface of the eye of the tiny moth Leucoptera coffeella. Antireflective coatings in larger insects with flatter facets often take the form of corneal nipples. However, evidence is presented that in an insect whose eyes have to operate near the lower diffraction limit and possess strongly convexly-curved corneae a radial arrangement of microridges is just as effective as nipples--and simpler to construct.