Prognostic Nomograms Predicting Risk of Keratoconus in Very Asymmetric Ectasia: Combined Corneal Tomographic and Biomechanical Assessments.

Xiaoyu Zhang,Yishan Qian,Ling Sun,Tian Han,Xingtao Zhou,Lan Ding,Yangyi Huang

doi:10.3389/fbioe.2022.839545

Abstract

Purpose: The aim of the study was to develop and validate a prognostic nomogram for subclinical keratoconus diagnosis using corneal tomographic and biomechanical integration assessments. Design: This is a retrospective case–control study. Methods: Setting: The study was carried out in a hospital setting. Patients: The study included patients with very asymmetric ectasia (VAE) and normal controls. Patients with VAE had defined clinical ectasia in one eye and normal topography (VAE-NT) in the fellow eye, and VAE-NT eyes were selected for analysis. VAE-NT was defined as stratified stage 0 using the ABCD keratoconus grading system. The normal control group was selected from corneal refractive surgery candidates at our clinic, and the right eye was enrolled. Observation Procedures: Scheimpflug-based corneal tomography (Pentacam) and corneal biomechanical assessment (Corvis ST) were performed. Main Outcome Measures: We performed multiple logistic regression analysis and constructed a simple nomogram via the stepwise method. The receiver operating characteristic (ROC) curve and discrimination and calibration of prognostic nomogram were performed by 500 bootstrap resamplings to assess the determination and clinical value, respectively. Results: A total of 59 VAE-NT and 142 normal eyes were enrolled. For differentiating normal and VAE-NT eyes, the values of specificity, sensitivity, and area under the ROC (AUROC) were 0.725, 0.610, and 0.713 for tomographic parameters, 0.886, 0.632, and 0.811 for biomechanical parameters, and 0.871, 0.754, and 0.849 for combined parameters, respectively. Combined parameters showed better predictability than separated tomographic or biomechanical parameters. Conclusion: Our nomogram developed with combined tomographic and biomechanical parameters demonstrated a plausible, capable, and widely implementable tool to predict risk of keratoconus. The identification of at-risk patients can provide advanced strategies to epitomize ectasia susceptibility.

Highlights

Detection of keratoconus is mandatory in candidates for corneal refractive surgery in order to avoid postoperative ectasia and for increased safety in corneal refractive surgery (Binder et al, 2005; Ambrosio and Randleman 2013)
Our nomogram developed with combined tomographic and biomechanical parameters demonstrated a plausible, capable, and widely implementable tool to predict risk of Prognostic Nomogram for Keratoconus keratoconus
Corvis ST (OCULUS Optikgeräte GmbH, Wetzlar, Germany) monitors corneal dynamic deformation due to a constant-pressure air pulse using an ultrahigh-speed Scheimpflug camera, and the latest improvement has been the combination of tomographic and biomechanical data derived from Scheimpflug analyses (Pentacam and Corvis ST; OCULUS Optikgeräte GmbH) (Nemeth et al, 2013; Ali et al, 2014)

Summary

Introduction

Detection of keratoconus is mandatory in candidates for corneal refractive surgery in order to avoid postoperative ectasia and for increased safety in corneal refractive surgery (Binder et al, 2005; Ambrosio and Randleman 2013). The gold standards for screening keratoconus are topographic and tomographic analyses, which are used to detect alterations in corneal morphology, such as thinning, increased curvature, or elevated corneal elevation (de Sanctis et al, 2008; Mihaltz et al, 2009). Previous studies, which sparked interest in corneal biomechanical assessment, found that biomechanical changes may occur even before tomographic changes (Kozobolis et al, 2012; Tian et al, 2014; Vinciguerra et al, 2016) may appear, and that early diagnosis of biomechanical disorders may provide a new way of detecting forme fruste keratoconus and other ectatic corneal diseases. The tomography biomechanical index (TBI) calculated by Pentacam and Corvis ST parameters has provided the possibility of discriminating the tomographical normal eyes from subclinical keratoconus eyes (Vinciguerra et al, 2016; Ambrósio et al, 2017; Ferreira-Mendes et al, 2019)

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