Early diagnosis of keratoconus: what difference is it making?

Abstract

In corneal refractive surgery, early diagnosis of keratoconus (subclinical asymptomatic keratoconus) is of great importance in patients seeking surgery because it can prevent progression of the pathology after surgery and make it symptomatic (corneal ectasia), thus creating the need for diagnostic tests that provide high sensitivity (ability to detect the disease in affected subjects) with the objective that no asymptomatic subclinical keratoconus ends up not being diagnosed and thus not undergo corneal refractive surgery. Recently, Uçakhan et al1 investigated several Pentacam parameters in subclinical keratoconus, keratoconus and normal eyes. They found that the Scheimpflug system could differentiate between ectatic and normal eyes. In this study, the optimum cut-off point for posterior elevation was found to be 26.5 µm (97.7% sensitivity and 81.0% specificity). In a study by Mihaltz et al2, receiver operating characteristic (ROC) curve analysis indicated that posterior elevation was the most important criterion in the diagnosis of keratoconus. A threshold value of 15.5 µm had sensitivity of 95.1% and specificity of 94.3% for differentiating normal eyes from keratoconus. These authors found lower pachymetry readings in subclinical, early and moderate keratoconus; however, they did not find significant differences in these parameters between subclinical keratoconus and normal eyes.