Biomechanical properties of early keratoconus: Suppressed deformation signal wave.

PURPOSE: To examine the diagnostic validity of different corneal biomechanical parameters for the detection of early keratoconus METHODS: Sixty-one eyes with a diagnosis of early keratoconus and 61 topographically normal eyes were enrolled in the study. All participants underwent testing with the Ocular Response Analyzer (ORA), and 40 indices from each cornea were included in the analysis.

RESULTS: The mean (standard deviation: SD) of keratometry and central corneal thickness in keratoconic corneas was 46.9 (2.5) diopter (D) and 473 (31) μm, respectively. Of the 40 evaluated indices, 32 showed a significant difference between the two groups using t-test (p<0.05). According to the results of logistic regression, the indices of height from the lowest to the highest point in peak 2 (H2(1)) and corneal resistance factor (CRF) with R(2)=0.79 were the best predictors of early keratoconus (p<0.001). H2(1) ≤190 with a sensitivity and specificity of 87% and 91.8%, respectively, and CRF≤8.6 with sensitivity and specificity of 87% and 85.3%, respectively, yielded an overall diagnostic accuracy of 97.3%.

CONCLUSION: This study results point to the important role of novel waveform-derived indices measured by ORA, along with conventional biomechanical indices, for the early diagnosis of keratoconus. The best predictors of keratoconus in its early stages are H2(1) and CRF which showed very high sensitivity and specificity for the detection of early keratoconus.