Evaluation of the Relationship Between the Changes in the Corneal Biomechanical Properties and Changes in the Anterior Segment OCT Parameters Following Customized Corneal Cross-Linking

Abstract

Purpose: This study aimed to investigate the relationship between changes in corneal biomechanical properties and changes in anterior segment optical coherence tomography (AS-OCT) parameters preoperatively and following customized corneal cross-linking (C-CXL) in eyes with progressive keratoconus.

Patients and methods: This study included 44 eyes of 44 patients (33 men, 11 women; average age 22.8 ± 6.4 years) who underwent C-CXL for progressive keratoconus. Scheimpflug-based tonometer (SBT) and AS-OCT findings were evaluated preoperatively and 3 months following CXL. Parameters related to changes in SBT parameters were examined by multiple regression analysis using the stepwise method.

Results: Regarding SBT parameters, significant changes were observed in the integrated area under the curve of the inverse concave radius (pre, 12.19 ± 1.95/mm; post, 11.26 ± 1.89/mm; p < 0.0001), maximum inverse radius (pre, 0.24 ± 0.04/mm; post, 0.23 ± 0.04/mm; p = 0.0053), deformation amplitude ratio max 2 mm (pre, 5.53 ± 0.81; post, 5.29 ± 0.71; p = 0.0048), and stress-strain index (pre, 0.74 ± 0.16; post, 0.84 ± 0.20; p < 0.0001), pre and post C-CXL. Regarding AS-OCT parameters, significant changes were observed in average keratometry (pre, 47.87 ± 3.61 D; post, 47.56 ± 3.29 D, p = 0.0104), steep keratometry (pre, 49.61 ± 4.01 D; post, 49.25 ± 3.59 D; p = 0.0115), maximum keratometry (pre, 55.44 ± 6.22 D; post, 54.68 ± 5.56 D; p = 0.0061), and thinnest corneal thickness (pre, 450.43 ± 41.74 μm; post, 444.00 ± 39.35 μm; p < 0.0001), pre and post C-CXL. Multiple regression analysis demonstrated that when the change in the deformation amplitude (DA) ratio max (2 mm) was the dependent variable, age, change in average keratometry, and change in the thinnest corneal thickness were selected as explanatory variables. When changes in the stiffness parameter at applanation 1 and stress-strain index were the dependent variables, change in the intraocular pressure (IOP) was selected as the explanatory variable.

Conclusion: Change in the SBT parameters following C-CXL could be related to the age, change in the IOP value, change in average keratometry, and thinnest corneal thickness.

Keywords: corneal biomechanics; corneal tomography; customized corneal cross-linking; keratoconus.

Figure 1

Correlation between Δcorneal biomechanical parameters and other parameters. A moderate positive correlation was found between the Δdeformation amplitude (DA) ratio max (2 mm) and age (A) (R=0.305, p=0.044). No significant correlation was found between the ΔDA Ratio Max (2 mm) and Δaverage K (B) (R=0.228, p=0.137). No significant correlation was found between the ΔDA Ratio Max (2 mm) and Δthinnest (C) (R=−0.265, p=0.083). A moderate positive correlation was found between the Δstiffness parameter at applanation 1 (SP-A1) and Δintraocular pressure (IOP) (D) (R=0.332, p=0.028). A moderate positive correlation was found between the Δstress-strain index (SSI) and ΔIOP (E) (R=0.308, p=0.042).

Figure 2

Correlation between each anterior segment optical coherence tomography (AS-OCT) parameter change and Δintegrated radius. No significant correlation was found between the change in each AS-OCT parameter and Δintegrated radius. ((A) Δaverage K, R=0.071, p=0.648) ((B) Δsteep K, R=0.147, p=0.342) ((C) Δcylinder, R=0.117, p=0.449) ((D) Δmaximum keratometry [Kmax], R=0.180, p=0.242) ((E) Δthinnest, R=−0.138, p=0.370).

Figure 3

Correlation between each anterior segment optical coherence tomography (AS-OCT) parameter change and Δ maximum (Max) inverse radius. No significant correlation was found between the change in each AS-OCT parameter and ΔMax inverse radius. ((A) Δaverage K, R=0.027, p=0.863) ((B) Δsteep K, R=0.029, p=0.854) ((C) Δcylinder, R=0.017, p=0.912) ((D) Δ maximum keratometry [Kmax], R=0.025, p=0.872) ((E) Δthinnest, R=−0.147, p=0.340).

Figure 4

Correlation between each anterior segment optical coherence tomography (AS-OCT) parameter change and ΔDA ratio max (2 mm). No significant correlation was found between the change in each AS-OCT parameter and Δ deformation amplitude (DA) ratio max (2 mm). ((A) Δaverage K, R=0.228, p=0.137) ((B) Δsteep K, R=0.196, p=0.201) ((C) Δcylinder, R=0.075, p=0.628) ((D) Δ maximum keratometry [Kmax], R=0.216, p=0.159) ((E) Δthinnest, R=−0.265, p=0.083).

Figure 5

Correlation between each anterior segment optical coherence tomography (AS-OCT) parameter change and Δ stiffness parameter at applanation 1 (SP-A1). No significant correlation was found between the change in each AS-OCT parameter and ΔSP-A1. ((A) Δaverage K, R=−0.030, p=0.848) ((B) Δsteep K, R=−0.038, p=0.805) ((C) Δcylinder, R=−0.018, p=0.905) ((D) ΔKmax, R=−0.028, p=0.858) ((E) Δthinnest, R=0.47, p=0.762).

Figure 6

Correlation between each anterior segment optical coherence tomography (AS-OCT) parameter change and Δ stress-strain index (SSI). No significant correlation was found between the change in each AS-OCT parameter and ΔSSI. ((A) Δaverage K, R=−0.036, p=0.818) ((B) Δsteep K, R=−0.022, p=0.888) ((C) Δcylinder, R=−0.017, p=0.913) ((D) Δ maximum keratometry [Kmax], R=−0.111, p=0.474) ((E) Δthinnest, R=0.38, p=0.806).