title: Comparison of keratometric and pachymetric parameters with Scheimpflug imaging in normal and keratoconic Asian eyes.
abstract: OBJECTIVE
  To evaluate the keratometric and pachymetric parameters of keratoconic corneas of Asian eyes with the Scheimpflug imaging camera.
  
  
  METHODS
  This is a cross-sectional study of 22 eyes with Amsler-Krumeich stage 1 keratoconus and 48 eyes from normal subjects conducted in a tertiary eye hospital. A rotating Scheimpflug imaging system, the Pentacam, was used to evaluate all eyes for tomographic parameters, as well as pachymetric progression indices (PPI) and Ambrósio relational thickness (ART).
  
  
  RESULTS
  All PPI and ART parameter values were significantly different between study and control groups. Cornea minimum radius of curvature, absolute distance from corneal apex to thinnest location, as well as the distance from corneal apex to thinnest location in Y-axis also demonstrated statistically significant differences. The mean ART values for keratoconus eyes were 241 μm (ART-maximum) and 352 μm (ART-average), falling within previously reported best cutoff values for detecting keratoconus. On receiver operating characteristics curve analysis, the area under the curve values were highest for PPI and ART parameters.
  
  
  CONCLUSIONS
  There are significant differences in tomographic parameters between stage 1 keratoconic and normal Asian eyes. Pachymetric indices such as the PPI and the ART index can serve as additional tools in differentiating keratoconic from normal eyes. The findings validate the usefulness of the ART in identifying keratoconic eyes in Asians.
authors.affiliation: Singapore National Eye Centre, Singapore.
authors.forename: Hou-Boon
authors.initials: HB
authors.lastname: Lim
authors.affiliation: Singapore National Eye Centre, Singapore.
authors.forename: Gavin S
authors.initials: GS
authors.lastname: Tan
authors.affiliation: Singapore National Eye Centre, Singapore.
authors.forename: Li
authors.initials: L
authors.lastname: Lim
authors.affiliation: Singapore Eye Research Institute, Singapore.
authors.forename: Hla Myint
authors.initials: HM
authors.lastname: Htoon
keywords: Ambrósio relational thickness; corneal tomography; keratoconus; pentacam