Posterior corneal astigmatism changes in cases with keratoconus

ABSTRACT

Background: keratoconus is bilateral [usually asymmetrical], progressive, non inflammatory, cone like anterior protrusion of the cornea involving the central and the inferior para central areas that results in corneal ectasia, astigmatism and diminution of vision. It usually seen after puberty, with incidence of 1 in 2000 of general population, the major benefit of corneal tomography is the measurement of the posterior corneal surface, because the posterior surface contributes minimally to the overall refractive power of the eye [due to the minimal difference between the index of refraction of the cornea and aqueous] it was considered less important both diagnostically and therapeutically. The posterior cornea, however, is an earlier indicator of ectatic change or ectasia susceptibility