Differences in Posterior Corneal Features Between Normal Corneas and Subclinical Keratoconus

Area of Science:

• Ophthalmology
• Corneal Imaging
• Keratoconus Detection

Background:

• Subclinical keratoconus detection is crucial for preventing post-refractive surgery ectasia.
• Traditional methods often rely on anterior corneal topography, which may miss early changes.
• Posterior corneal morphology is increasingly recognized as a key indicator in keratoconus progression.

Purpose of the Study:

• To evaluate the diagnostic capability of posterior corneal parameters obtained via a Placido dual-Scheimpflug analyzer.
• To compare the discriminating power of different posterior corneal features for differentiating normal from subclinical keratoconus.
• To identify the most sensitive posterior corneal metrics for early keratoconus detection.

Main Methods:

• Retrospective analysis of 79 normal eyes and 39 eyes with clinical keratoconus (fellow eyes).
• Corneal imaging performed using a Placido dual-Scheimpflug system.
• Posterior surface variables (curvature, elevation, asymmetry, eccentricity) analyzed and compared between groups.
• Receiver operator characteristics (ROC) curves used to assess discriminating ability.

Main Results:

• Asymmetry and elevation parameters of the posterior cornea showed statistically significant differences between normal and keratoconus groups (P < .05).
• Curvature and eccentricity parameters were not significantly different.
• Maximum posterior elevation and asphericity asymmetry index demonstrated high discriminating ability (AUC 0.877 and 0.871, respectively).

Conclusions:

• Dual-Scheimpflug analysis of the posterior cornea provides valuable parameters for differentiating normal corneas from subclinical keratoconus.
• Posterior corneal asymmetry and elevation are the most sensitive indicators for distinguishing these two populations.
• These findings support the use of posterior corneal analysis in early keratoconus screening.