corneal facet

cor·ne·al fac·et

a corneal depression following loss of stroma.

corneal facet 

1. Small flattened depression on the outer surface of the cornea, due to a healed ulcer which has failed to fill with tissue.
2. The corneal element in the ommatidium of the compound eye. See compound eye; corneal ulcer.
References in periodicals archive ?
Because photon catch is proportional to the cross-sectional area of ommatidial corneal facets, a single Limulus ommatidium (0.