[Application of the Brillouin optical scanning system to investigate the biomechanical properties of the myopic lens and their changes before and after cycloplegia].

Objective: To investigate the biomechanical properties of the lens and the changes before and after cycloplegia in the myopic population in China, and to analyze the possible influencing factors. Methods: This is a cross-sectional study. Consecutively, 159 myopic patients (159 right eyes) who underwent the Brillouin Optical Scanning System examination from November 2023 to May 2024 at Tianjin Eye Hospital were recruited. Among them, 82 were male and 77 were female, with an age of 21 (18, 24) years. The patients were classified into low, intermediate, and high myopia groups according to the equivalent spherical lens power. The lens biomechanical parameters, as well as ocular refractive and morphological parameters, were measured, including the width of top plateau, the width of bottom plateau, the longitudinal modulus of nucleus (LMN), the longitudinal modulus of cortex (LMC), the axial length of the eye, lens thickness, anterior radius of curvature, posterior radius of curvature, and lens density. The differences in lens parameters before and after cycloplegia were compared. Univariate and multivariate linear regression analyses were utilized to assess the factors associated with the LMN before and after cycloplegia. Results: There were 46, 59, and 54 patients in the low, intermediate, and high myopia groups respectively. There were no statistically significant differences in age or gender distribution among the three groups (all P>0.05). The LMN of the three groups of low, intermediate, and high myopia were 3.383 (3.361, 3.411), 3.401 (3.378, 3.416), and 3.415 (3.395, 3.422) GPa, respectively, and the LMN was higher in the high myopia group; the difference in the LMN among the three groups was statistically significant (P<0.001). The difference in the LMC of the lens cortex was not statistically significant among the 3 groups of low, intermediate, and high myopia (P>0.05). After ciliary muscle paralysis, the LMN decreased slightly compared with that before paralysis [3.395 (3.371, 3.414) and 3.405 (3.379, 3.417) GPa, P<0.05]. The results of multifactorial linear regression analysis showed that LMN was proportional to refractive error both before and after ciliary muscle paralysis, and the higher the myopia, the greater the LMN (all P<0.05). The greater the lens optical density, the smaller the LMN (all P<0.05). Gender was also associated with LMN (all P<0.05). Conclusions: In young myopic patients, LMN increased with the increase of myopia degree and was higher in highly myopic patients, suggesting that the biomechanical properties of the myopic lens may be altered. Moreover, there were differences in LMN before and after ciliary muscle paralysis, suggesting that accommodation may affect the mechanical properties of the lens. Gender and lens optical density are also relevant factors affecting LMN.