Mild Keratoconus or Corneal Warpage: Differentiation of Topographic Inferior Steepening Based on Corneal Tomography Data
Purpose
To demonstrate the relevance of going beyond corneal surface topography when evaluating cases with suspicious asymmetric bow tie and inferior steepening (ABT/IS) on topographic curvature maps; and to test the ability of corneal tomographic data for distinguishing from contact-lens related corneal warpage and mild keratoconus.
Methods
Report of two cases. Completed ophthalmic examination including Placido-disk based corneal topography (Oculus Keratograph 4) and rotating Scheimpflug corneal and anterior segment tomography (Oculus Pentacam HR, Wetzlar, Germany).
Results
The topographic evaluations with reflection (Placido) and projection (Scheimpflug) showed similar results in both cases. There was a pattern of inferior steepening in both cases, consistent with suspicious of keratoconus. In the first case, the maximal keratometric value was 43.2D and the overall deviation value from the Belin/Ambrósio Enhanced Ectasia Display (BAD-D) was 1.76 in the study eye (OD), while the BAD-D was 6.59 in the fellow eye, which had the clinical findings consistent with keratoconus (KC) stage 2. The second case presented with Kmax of 45.2D and BAD-D of 0.76 in OD and 1.01 in OS. This patient had discontinued the use of soft contact lens wear less than 1 day prior to the exam.
Conclusion
Corneal tomographic data allowed us to distinguish mild or forme fruste keratoconus (FFKC) and contact lens-induced corneal warpage, while similar findings were observed on curvature maps.