Assessment of Keratoconus Risk in Very Asymmetric Ectasia Using Corneal Tomographic and Biomechanical Parameters

Abstract

Purpose

To investigate the relationship between corneal tomographic or biomechanical parameters and risk of keratoconus in very asymmetric ectasia (VAE).

Methods

This retrospective case-control single-centre study included patients with VAE and normal controls. The VAE group had clinical ectasia in one eye and normal topography (VAE-NT) in the fellow eye; VAE-NT eyes were selected for analysis. The control group was selected from corneal refractive surgery candidates; the right eye was enrolled. Scheimpflug-based corneal tomography (Pentacam) and corneal biomechanical assessment (Corvis ST) were performed. Univariate and multivariable logistic regression were performed using Cox proportional hazards models to evaluate keratoconus-associated risk factors. A two-piecewise linear regression model was applied to examine the threshold effect of selected vital paragmeters on the risk of keratoconus according to a smoothing plot.

Results

Threshold effect between tomographic integration and risk of keratoconus was observed. Discrepancy between the central corneal thickness and thinnest corneal thickness (discrepancy CCT vs TCT) greater than 5 μm, discrepancy between the apex corneal thickness and thinnest corneal thickness (discrepancy ACT vs TCT) greater than 3 μm, vector distance between CCT and TCT (distance CCT vs TCT) greater than 0.65 mm indicated a significant increased risk of keratoconus. Risk of keratoconus decreased when distance CCT vs TCT was less than 0.65 mm.

Conclusion

Discrepancy CCT vs TCT, discrepancy ACT vs TCT, and distance CCT vs TCT can be used as indicators for risk assessment of early keratoconus.

Keywords:

• keratoconus
• corneal tomographic
• corneal biomechanical
• very asymmetric ectasia

Data Sharing Statement

Data is available on request from the corresponding author.

Compliance with Ethics Guidelines

The Ethics Committee of the Eye and ENT Hospital of Fudan University approved this study (approval number 2021118-1). This study adhered to the tenets of the Declaration of Helsinki. All participants provided informed consent.

Disclosure

The authors declare that there are no competing interests. Yishan Qian and Xingtao Zhou contributed equally to the work and should therefore be regarded as equal corresponding authors.

Additional information

Funding

This study was supported by the National Natural Science Foundation of China (Grant No. 82371096), Joint Research Project of New Frontier Technology in Municipal Hospitals (SHDC12018103), Project of Shanghai Science and Technology (Grant No.20410710100), Clinical Research Plan of SHDC (SHDC2020CR1043B), and Project of Shanghai Xuhui District Science and Technology (XHLHGG202104).