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Purpose: To report age?related variations in corneal stress–strain index (SSI) in healthy Indians. Methods: It was a retrospective study where healthy Indian individuals aged between 11 and 70 years who had undergone corneal biomechanics assessment using Corvis ST between January 2017 and December 2021 were enrolled. Composite corneal biomechanical parameters and corneal SSI were abstracted from Corvis ST and compared across different age groups using one?way analysis of variance (ANOVA). Also, Pearson’s correlation was used to evaluate the association between age and SSI. Results: Nine hundred and thirty?six eyes of 936 patients with ages between 11 and 77 years with mean ± SD intraocular pressure (IOP) and pachymetry of 16.52 ± 2.10 mmHg and 541.13 ± 26.39 ?s, respectively. Composite corneal biomechanical parameters such as deformation amplitude ratio max at 1 mm (P < 0.001) and 2 mm (P < 0.001), biomechanically corrected IOP (P = 0.004), stiffness parameter at A1 (P < 0.001, Corvis biomechanical index (P < 0.018), and SSI (P < 0.001) were found to be significantly different as a function of age group. We noted a statistically significant positive association of SSI with age (P < 0.001), spherical equivalent refractive error (P < 0.001), and IOP (P < 0.001) and a significant negative association with anterior corneal astigmatism (P < 0.001) and Anterior chamber depth (ACD) (P < 0.001). Also, SSI was positively associated with SPA1 and bIOP, whereas negatively associated with integrated radius, max inverse radius, and Max Deformation amplitude (DA) ratio at 1 mm and 2 mm. Conclusion: We noted a positive association of corneal SSI with age in normal healthy Indian eyes. This information could be helpful for future corneal biomechanical research.
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AIM:To assess the anterior corneal astigmatism (ACA)and posterior corneal astigmatism (PCA) patterns across various age groups.We also evaluated the association between magnitudes and axes of the ACA and PCA across these age groups.METHODS:The present study was a cross-sectional analysis of clinical data of 381 eyes.We converted the clinical astigmatic notation to vector notation for analysis of ACA and PCA.We estimated the correlation between magnitude and axes of the ACA and PCA in the whole population and in four age groups (5-19,20-39,40-59,and ≥ 60y).We used random effects linear regression models for estimating the association between the magnitudes of ACA and PCA.RESULTS:The mean of the magnitude of the ACA (3.59D) and the PCA (0.50D) was highest in children (5 to 9y).Overall,the magnitude of the ACA ranged from 0D to 10.0 Diopters (D) and the magnitude of the PCA ranged from 0 to 3.5 D.There was a significant correlation between the ACA and the PCA in the younger age group (r=0.85,P＜0.001).In those 60y or older,the PCA increased by 0.04 units (95％ confidence intervals:0.005,0.07;P=0.03) with each unit increase in the ACA,the increase was the smallest in this age group.CONCLUSION:It will be prudent to measure the both the magnitude and axis of the PCA,particularly in those above 60y rather than rely on rule-of-thumb calculations based on ACA parameters for IOL power calculation.