Abstract
Purpose: To review the role of corneal biomechanics for the clinical evaluation of patients with ectatic corneal diseases. Methods: A total of 1295 eyes were included for analysis in this study. The normal healthy group (group N) included one eye randomly selected from 736 patients with healthy corneas, the keratoconus group (group KC) included one eye randomly selected from 321 patients with keratoconus. The 113 nonoperated ectatic eyes from 125 patients with very asymmetric ectasia (group VAE-E), whose fellow eyes presented relatively normal topography (group VAE-NT), were also included. The parameters from corneal tomography and biomechanics were obtained using the Pentacam HR and Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany). The accuracies of the tested variables for distinguishing all cases (KC, VAE-E, and VAE-NT), for detecting clinical ectasia (KC + VAE-E) and for identifying abnormalities among the VAE-NT, were investigated. A comparison was performed considering the areas under the receiver operating characteristic curve (AUC; DeLong’s method). Results: Considering all cases (KC, VAE-E, and VAE-NT), the AUC of the tomographic-biomechanical parameter (TBI) was 0.992, which was statistically higher than all individual parameters (DeLong’s; p < 0.05): PRFI- Pentacam Random Forest Index (0.982), BAD-D- Belin -Ambrosio D value (0.959), CBI -corneal biomechanical index (0.91), and IS Abs- Inferior-superior value (0.91). The AUC of the TBI for detecting clinical ectasia (KC + VAE-E) was 0.999, and this was again statistically higher than all parameters (DeLong’s; p < 0.05): PRFI (0.996), BAD-D (0.995), CBI (0.949), and IS Abs (0.977). Considering the VAE-NT group, the AUC of the TBI was 0.966, which was also statistically higher than all parameters (DeLong’s; p < 0.05): PRFI (0.934), BAD- D (0.834), CBI (0.774), and IS Abs (0.677). Conclusions: Corneal biomechanical data enhances the evaluation of patients with corneal ectasia and meaningfully adds to the multimodal diagnostic armamentarium. The integration of biomechanical data and corneal tomography with artificial intelligence data augments the sensitivity and specificity for screening and enhancing early diagnosis. Besides, corneal biomechanics may be relevant for determining the prognosis and staging the disease.
Highlights
Understanding the material and structural properties of the cornea has gained increased clinical utility over the latest decades
We describe two main Corvis ST parameters developed by this group for enhancing ectasia detection, the corneal biomechanical index (CBI), and the tomographic-biomechanical parameter (TBI)
0.992, which was statistically higher than Pentacam random forest index (PRFI) (0.982), Belin–Ambrosio Display D value (BAD-D) (0.959), CBI (0.91), IS Abs (0.91), Topographic Keratoconus classification index (TKC)
Summary
Understanding the material and structural properties of the cornea has gained increased clinical utility over the latest decades. In the field of refractive surgery, the investigation of corneal biomechanical properties turned out to be a very relevant part of the screening process, in an attempt to identify patients at higher risk (susceptible) to develop iatrogenic ectasia after laser vision correction (LVC) [9,10,11]. Due to unsatisfactory quality of vision with glasses and contact lenses, patients with keratoconus (KC) and other ectatic disorders, with subclinical disease, frequently present as refractive surgery candidates. These cases typically have from less optimal to poor results after LVC and are at very high risk for iatrogenic ectasia development after the surgical procedure [12,13]. The advent of collagen crosslinking and other treatment modalities such as intracorneal ring segments (ICRS) has made relevant the identification of milder or subclinical forms of ectatic corneal diseases along with monitoring the disease progression [14,15]
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