Correlation of 3-Dimensional Epithelial Thickness Variability in Healthy and Keratoconic Eyes
Narrative Responses:
Purpose
To evaluate repeatability, accuracy and precision, as well as the clinical feasibility of in vivo measurement of epithelial thickness and epithelial topographic variability in a large cohort of healthy and keratoconic eyes by spectral domain optical coherence tomography (AS-OCT), and to compare with Scheimpflug imaging keratoconus severity.
Methods
250 healthy (group A) and 155 untreated keratoconic (Group Β) eyes were subjected to anterior segment OCT three-dimensional epithelial thickness imaging. Comparative statistical analysis of patterns was performed, investigating central, minimum, inferior, posterior, and topographic variability of epithelial thickness. Epithelial thickness characteristics were correlated to established Scheimpflug imaging–derived keratoconus classification and anterior surface irregularity indices.
Results
Intra-individual repeatability of epithelial thickness was for group A ±1.13 μm, for group B ±1.78 μm for center and average ±1.67 μm (center, superior, inferior, maximum and minimum). In group A, center epithelial was 52.54±3.23 μm, maximum 55.33±3.27 μm and minimum 48.50±3.98 μm. In group B, center thickness was 51.75±7.02 μm, maximum and minimum were 63.54±8.85 μm and 40.73±8.51 μm. Topographic variability was 6.07±3.55 μm (range -22.81±12.55 μm) for the keratoconic group, while for the control group 1.59±0.79 μm (-6.86±3.33 μm). Both epithelial thickness variability and range were increased with keratoconus severity and correlated well with keratoconus severity.
Conclusion
AS-OCT epithelial thickness measurement in keratoconus had high predictability. Compared to normal, particularly in lower stages of keratoconus, increased topographic thickness variability and range correlated remarkably with keratoconus severity, obtained by established Scheimpflug imaging-derived anterior-surface irregularity indices.