Posterior corneal astigmatism changes in cases with Keratoconus

Abstract

Keratoconus is a bilateral, degenerative, non- inflammatory, progressive thinning of the cornea that results in apical protrusion (ectasia), resulting in a high degree of irregular myopic astigmatism. It is the most common corneal ectasia of incidence (1 in 2000), usually starts at puberty, and typically progresses until the fourth decade oflife. Diagnosis of keratoconus has greatly improved from simple clinical diagnosis with the advent of better diagnostic devices like corneal topographers based on placido disc, elevation based topographers with assessment of both anterior and posterior cornealsurfaces. Pentacam provide different curvature (e.g. mean K,K max, skewing), elevation ( e.g. anterior and posterior elevation at thinnest location) and thickness parameters (e.g. thickness profile and PPI) as well as topometric indices (ISV, IHD) which help in diagnosis of KC.