Combining Ocular Response Analyzer Metrics for Corneal Biomechanical Diagnosis

Abstract

In biomechanical keratoconus screening, some non-keratoconic myopic eyes show altered ocular biomechanical properties and are identified as false-positive cases. The low specificity of DifCRF when dealing with these non-keratoconic eyes could be improved by considering additional biomechanical descriptors such as DifCH and CH-CRF, which seem to be indicative of the aforementioned biomechanical profile.

Multivariate Analysis of the Ocular Response Analyzer’s Corneal Deformation Response Curve for Early Keratoconus Detection

“…The actual performance for both indices was remarkably lower than that reported by Mikielewicz et al [ 4 ], and this difference reflects the subclinical nature of our keratoconic eyes. A combined score (BiomechScore) that considered both corneal-thickness-corrected CRF and the difference between CH and CRF (CH-CRF) had slightly better results, as we have previously shown [ 5 ]. Such approach works better when dealing with myopic eyes, which also have reduced CRF values (just as keratoconic eyes) but markedly negative CH-CRF values (keratoconic eyes have positive CH-CRF values).…”

“…The methodology for calculating central-corneal-thickness-corrected CH (ccCH) and CRF (ccCRF) was reported elsewhere [ 9 ] and that for CH-CRF was published by Touboul et al [ 18 ]. The combination of ccCRF and CH-CRF through logistic regression, termed biomechanical score (BiomechScore), has also been thoroughly described [ 5 ]. Factor analysis was performed on all biomechanical descriptors from both groups combined with principal components analysis as extraction method and varimax as rotation method.…”

“…The release of the Ocular Response Analyzer (ORA) device in 2005 made corneal biomechanical testing clinically possible [ 1 ], and many potential uses for this new technology have since been proposed. Among them, early detection of keratoconus and of corneas at risk of developing post-refractive-surgery ectasia is perhaps the most widely explored application in the literature [ 2 – 5 ]. The ORA brought along new corneal indices that attempted to describe the deformation response curve to a controlled air puff, which can readily be obtained from the software: corneal hysteresis (CH) and corneal resistance factor (CRF) [ 6 , 7 ].…”

“…Insufficient knowledge of the many factors that affect corneal biomechanical testing led investigators to simply compare CH and CRF between control subjects and keratoconic patients and thus conclude that they performed poorly at disease detection. However, more recently we have shown that acceptable diagnostic capacity can be obtained by correcting those measurements for corneal thickness [ 3 ], one of the most influential factors, and that the results can be further improved by combining corneal compensated CRF and the difference between CH and CRF [ 5 ].…”

Bilateral symmetry in vision and influence of ocular surgical procedures on binocular vision: A topical review

“…All these possibilities suggest that the future holds great potential for investigating the role of bilateral symmetry in the human vision and its influence in developing improved ocular surgical procedures. Particularly for preserving the bilateral symmetry in the eyes after laser based refractive procedures, biomechanical response of the cornea, 119 , 120 ablation centration, 112 epithelial thickness profile, 121 , 122 and the role of HOA of the cornea 117 should be extensively investigated.…”