Screening subclinical keratoconus with placido-based corneal indices

Area of Science:

• Ophthalmology
• Corneal Imaging
• Diagnostic Tools

Background:

• Keratoconus (KC) diagnosis relies on various clinical and topographic data.
• Existing methods may have limitations in early detection or grading.

Purpose of the Study:

• To evaluate novel topographic indices calculated directly from Placido ring images.
• To assess the diagnostic performance of these indices in normal, keratoconic, and suspect eyes.

Main Methods:

• A comparative study included 124 eyes from 106 patients (control, KC, KC suspect groups).
• Corneal topography was performed using a Placido-based CSO system.
• New irregularity indices were computed and their discriminating ability analyzed.

Main Results:

• Significant differences in index values were observed among the three groups (p<0.05).
• Receiver operating characteristic analysis and K-fold cross-validation confirmed the indices' discriminative power.
• The indices showed high sensitivity in detecting corneal irregularities, even in KC suspect eyes.

Conclusions:

• Direct analysis of Placido mire images provides a valid method for detecting corneal irregularities.
• The new indices are simple, sensitive, and effective for diagnosing and grading KC.
• These indices can serve as supplementary criteria to current keratometric classifications.