Purpose: This study aimed to investigate the correlation of axial length/corneal radius of curvature ratio with stress–strain index (SSI).Methods: Retrospective analysis was conducted to compare the right eyes of those with high myopia (HM, n = 132; age and 10–48 years) with those without high myopia (NHM, n = 135; age and 7–48 years), where the baseline axial length, corneal radius of curvature ratio, and central corneal thickness were analyzed; the differences in two groups were compared; and the relationship of axial length and axial length/corneal radius of curvature ratio with SSI were explored.Results: Compared with AL < 26mm, SSI significantly decreased when AL ≥ 26 mm (p = 0.001), while there was no correlation with AL in the NHM group (r = -0.14, p = 0.12) or HM group (r = -0.09, p = 0.32). AL/CR was significantly associated with SSI in both the NHM (r = -0.4, p < 0.001) and HM (r = -0.18, p = 0.04) groups. In the NHM group, AL/CR was significantly associated with SSI (unstandardized beta = -0.514, se = 0.109, p < 0.001) with the adjustment of age and gender. Additionally, a significant association of SSI with AL/CR was also found after adjusting for age and gender (unstandardized beta = -0.258, se = 0.096, and p = 0.0082) in the HM group.Conclusion: SSI showed a significant negative correlation with AL/CR in patients without high myopia and in patients with high myopia. However, SSI exhibited no decrease with the worsening of myopia, but it gradually remained stable at a low level. The findings of this study validate, to some extent, the possibility of analyzing the dynamic changes in ocular wall stiffness during the development of myopia by measuring in vivo corneal biomechanical parameters.

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 (ALMorgan) based on the mathematical equation proposed by Morgan. Second, we proposed an axial increment model (ΔAL) corresponding to spherical equivalent error (SER) based on ALemmetropia (ALMorgan at SER = 0) and subject’s real AL. Finally, we evaluated the variations of ΔAL with SSI changes based on the mathematical estimation model.Results: We found that AL was closely associated with ALMorgan (r = 0.91, t = 33.8, p < 0.001) with good consistency and SER was negatively associated with ΔAL (r = −0.89, t = −30.7, p < 0.001). The association of SSI with AL, ALemmetropia, and ΔAL can be summarized using the following equations: AL=27.7−2.04×SSI, ALemmetropia=23.2+0.561×SSI, and ΔAL=4.52−2.6×SSI. In adjusted models, SSI was negatively associated with AL (Model 1: β = −2.01, p < 0.001) and ΔAL (Model 3: β = −2.49, p < 0.001) but positively associated with ALemmetropia (Model 2: β = 0.48, p < 0.05). In addition, SSI was negatively associated with ΔAL among subjects with AL ≥ 26 mm (β = −1.36, p = 0.02).Conclusion: AL increased with decreasing SSI in myopia.