Abstract
Purpose :
Measuring corneal biomechanics with high spatial resolution may assist for subclinical keratoconus detection. Current instruments (Corvis ST and Ocular Response Analyzer) measure overall corneal stiffness but are incapable of resolving spatial variations in corneal stiffness. Optical coherence elastography (OCE) can spatially resolve corneal stiffness, which has the potential to improve keratoconus detection accuracy. Here we determine the sensitivity and specificity of OCE relative to existing instruments for keratoconus detection.
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Methods :
OCE measurements were performed on ten eyes from six keratoconus patients and ten eyes from six healthy sex-, age-, and race-matched subjects. Mechanical waves were induced in the corneas of these subjects using micro-liter air pulse stimulation, and the wave propagation was imaged using phase sensitive OCT. The speed of this laterally propagating mechanical wave was computed inside the keratoconic cone region defined by topography images. This wave speed was compared to the speed measured outside the keratoconus cone and to the speed measured in healthy subjects. Corvis biomechanical index (CBI) was computed from the dynamic corneal deformation images. Corneal hysteresis (CH) and corneal response factor (CRF) were obtained from ORA. Area underneath the receiver operating characteristic (ROC) curves was used to evaluate the classification accuracy of each parameter (wave speed, CBI, CH, and CRF) in detecting keratoconus.
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Results :
Wave speed was lower in the keratoconic cone regions (range:8.32 m/sec to 11.53 m/sec) compared to the speeds outside the cone regions (range, 10.92 m/sec to 14.9 m/sec) and in normal subjects (range:11.45 m/sec to 15.4 m/sec). The wave speed had the highest predictive accuracy (Sensitivity: 97%, Specificity: 97%) in distinguishing keratoconus eyes from normal eyes compared to CH (Sensitivity: 90%, Specificity: 94%), CRF (Sensitivity: 92%, Specificity: 94%) and CBI (Sensitivity: 92%, Specificity: 86%).
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Conclusions :
The results from the preliminary data suggest that mechanical wave speed can distinguish keratoconus eyes from normal eyes with high sensitivity and specificity. Localized biomechanical changes in the keratoconic corneas can be spatially quantified utilizing OCE.
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This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.