Novel Keratoconus Diagnosis and Progression Criteria Based on Multiple Anterior Segment Imaging Devices
Purpose
To evaluate keratoconus diagnosis and progression assessment based on modern anterior segment imaging modalities including Scheimpflug imaging, placido topography, anterior-segment optical coherence tomography (AS-OCT), and novel multi-colored spot reflection Topography (MSRT).
Methods
Two-hundred fifty keratoconic cases were evaluated for keratoconic grading and anterior surface indexing by Scheimpflug imaging (Oculyzer, WaveLight AG), Placido Topography (Vario Topolyzer, WaveLight AG), AS-OCT (RTVue-100, Optovue Inc.) and a newly-introduced MSRT (Cassini, i-Optics). The correlations between Scheimpflug- and Placido- derived keratoconic grading and anterior-surface irregularity indices for keratoconus, as well as epithelial thickness distribution characteristics were assessed with the AS-OCT and the MSRT-derived keratoconus indices employing paired two-tailed t-tests, Bland-Altman plots, coefficient of determination (r2), and trend line linearity.
Results
Excellent agreement among the Scheimpflug- and Placido- derived keratoconic grading and anterior-surface irregularity indices for keratoconus with the AS-OCT and the MSRT - derived keratoconus was observed. Increased topographic thickness variability and range was found to be in correlation with keratoconus severity, quantitatively expressed with Scheimpflug imaging-derived anterior-surface irregularity indices.
Conclusion
The quantitative anterior-segment topographic indices may help aid in early diagnosis, proper-monitoring and surgical follow-up in keratoconus by providing quantitative measure of ectasia progression. We present a benchmark for future studies for the development of keratoconus diagnosis, possibly providing an effective tool of post-operative cross-linking or other ectasia-management procedures monitoring.