Corneal elevation indices in normal and keratoconic eyes

Area of Science:

• Ophthalmology
• Corneal Imaging
• Biomedical Engineering

Background:

• Keratoconus is a progressive thinning of the cornea, leading to irregular astigmatism and vision impairment.
• Early detection of keratoconus and keratoconus-suspect eyes is crucial for timely intervention and management.
• Corneal elevation maps provide detailed topographical information for assessing corneal shape abnormalities.

Purpose of the Study:

• To identify a reliable index using Orbscan corneal elevation data to differentiate between normal, keratoconus, and keratoconus-suspect eyes.
• To establish the diagnostic accuracy of proposed indices in a clinical setting.

Main Methods:

• A retrospective, multicenter study analyzed corneal elevation data from normal subjects, keratoconus patients, and keratoconus suspects.
• Anterior and posterior best-fit sphere (BFS), anterior and posterior elevation, and keratometry values were assessed.
• Receiver operating characteristic (ROC) curves were used to determine indices with optimal sensitivity and specificity.

Main Results:

• The anterior elevation ratio (anterior elevation/anterior BFS) demonstrated high accuracy in classifying eyes.
• An anterior elevation ratio cutoff of 0.5122 mm or less achieved 99% sensitivity and 95.2% specificity for distinguishing normal from keratoconus/suspect eyes.
• Similar high diagnostic performance was observed in a validation cohort, including differentiating suspects from normal eyes.

Conclusions:

• Anterior corneal elevation parameters, particularly the anterior elevation ratio, are clinically significant for detecting keratoconus and suspect cases.
• These findings support the use of anterior elevation indices derived from corneal topography for early keratoconus diagnosis.