Effect of corneal stiffness decrease on axial length elongation in myopia determined based on a mathematical estimation model

Purpose: To investigate the relationship between the corneal material stiffness parameter stress-strain index (SSI) and axial length (AL) elongation with varying severities of myopia, based on a mathematical estimation model. Methods: This single-center, cross-sectional study included data from healthy subjects and patients preparing for refractive surgery in the Qingdao Eye Hospital of Shandong First Medical University. Data were collected from July 2021 to April 2022. First, we performed and tested an estimated AL model ( [Formula: see text] ) based on the mathematical equation proposed by Morgan. Second, we proposed an axial increment model ( [Formula: see text] ) corresponding to spherical equivalent error (SER) based on [Formula: see text] ( [Formula: see text] at SER = 0) and subject’s real AL. Finally, we evaluated the variations of [Formula: see text] with SSI changes based on the mathematical estimation model. Results: We found that AL was closely associated with [Formula: see text] (r = 0.91, t = 33.8, p < 0.001) with good consistency and SER was negatively associated with [Formula: see text] (r = −0.89, t = −30.7, p < 0.001). The association of SSI with AL, [Formula: see text] , and [Formula: see text] can be summarized using the following equations: [Formula: see text] , [Formula: see text] , and [Formula: see text] . In adjusted models, SSI was negatively associated with AL (Model 1: β = −2.01, p < 0.001) and [Formula: see text] (Model 3: β = −2.49, p < 0.001) but positively associated with [Formula: see text] (Model 2: β = 0.48, p < 0.05). In addition, SSI was negatively associated with [Formula: see text] among subjects with AL ≥ 26 mm (β = −1.36, p = 0.02). Conclusion: AL increased with decreasing SSI in myopia.