Combined biomechanical and tomographic keratoconus staging: Adding a biomechanical parameter to the ABCD keratoconus staging system

Abstract

Purpose: This retrospective cross-sectional study evaluated the potential of an additional biomechanical parameter 'E' as an addition to the tomographic ABCD ectasia/keratoconus (KC) staging. Methods:The Corvis Biomechanical Factor (CBiF) represents the modified linear term of the Corvis Biomechanical Index (CBI) developed based on 448 KC corneas from the Homburg Keratoconus Center (HKC). The CBiF range was divided into five stages (E0 to E4) to create a grading system according to the ABCD stages. Stage E0 was characterized by values smaller than the 2.5 percentile. The thresholds were created by dividing the CBiF range between the 2.5 and 97.5 percentiles into four groups of equal values (E1-E4). The frequency distribution of 'E' was analysed and independently validated based on another 860 KC corneas dataset from Milano and Rio de Janeiro (MR). The relationship between 'E' and the ABCD staging was analysed by crosstabulation. The specificity of 'E' was assessed based on healthy controls (112|851) from both datasets (HKC|MR).Results: 'E' was normally distributed with E0 = 37|30, E1 = 86|200, E2 = 155|354, E3 = 101|206, E4 = 69| 70 in the KC group and 96.4%|90.5% of the controls classified E0 in the HKC|MR dataset, respectively. Crosstabulation revealed that 'E' was most comparable to posterior corneal curvature ('B') in both datasets, while showing a trend towards more advanced stages in comparison to anterior corneal curvature ('A') and thinnest corneal thickness ('C'). Conclusion:The novel Corvis-derived parameter 'E' provides a biomechanical staging for ectasia/KC potentially enhancing the ABCD staging and may detect abnormalities before tomographic changes, which requires further studies.

Single-cell atlas of keratoconus corneas revealed aberrant transcriptional signatures and implicated mechanical stretch as a trigger for keratoconus pathogenesis

“…Several contemporary studies have also investigated the genomic, transcriptomic or proteomic alterations in keratoconus samples 6,17,18 , though stroma degradation were spotted, more multifaceted and precise signals in cell type-specific manners were diluted because of the limitation of bulkinput methods. In addition, previous studies demonstrated that keratoconus is often accompanied by altered biomechanical properties of the cornea, which can be an indicator of healthy and keratoconus eyes [19][20][21][22][23] . Multivariate analysis of risk factors for keratoconus determined that eye rubbing was the most significant predictor for the progression of keratoconus 24,25 .…”

Corvis Biomechanical Factor Facilitates the Detection of Primary Angle Closure Glaucoma

“…An interval spacing of 0.58 was defined for CBiF gates of each E-stage. 37 Lower CBiF values indicated higher E-stages. 37 Biomechanically corrected IOP was calculated from finite element simulations that were least affected by corneal properties.…”

“… 34 , 36 E-stage was defined by classifying CBiF into five stages (E0–E4) to rank the severity of corneal destablilization. 37 CBiF values ≥5.94 were designated as stage E0. An interval spacing of 0.58 was defined for CBiF gates of each E-stage.…”

Differential Diagnosis of Keratoconus Based on New Technologies

“…Prior to corneal curvature or thickness change due to the disease, the corneal stiffness and elasticity is already altered. Therefore, the measurement of biomechanical properties is crucial for the detection of subclinical cases, staging and differential diagnosis [40][41][42][43][44]. Most of the aforementioned parameters indicated that the biomechanical properties of normal and keratoconic eyes were significantly different [43][44][45].…”

“…Therefore, the measurement of biomechanical properties is crucial for the detection of subclinical cases, staging and differential diagnosis [40][41][42][43][44]. Most of the aforementioned parameters indicated that the biomechanical properties of normal and keratoconic eyes were significantly different [43][44][45]. Consequently, there is the assumption of a significantly smaller deformation of the central cornea in PMD corneas than in healthy corneas [46].…”