... , meeting each other at a point P. Their optical path length difference, ΔOPL=2 R [sin(α/2)] 2 + np {[sinα+sin( m α)]/sin[α(1+ m )]–1}(see Materials and methods), depends on the angle of incidence, or,equivalently, on the distance of the facets in the corneal lattice. To estimate the optical path lengths...