In Vivo Brillouin Analysis of Lens Nucleus and Cortex in Adult Myopic Eyes and Their Correlation With Accommodation

Purpose: The purpose of this study was to investigate the in vivo biomechanical properties of crystalline lens nucleus and cortex in adults with myopia, their potential influences, and the correlation between these properties and ocular accommodation. Methods: The study included 195 right eyes of 195 participants, divided into 4 groups based on spherical equivalent: emmetropia (37 eyes), low myopia (41 eyes), moderate myopia (59 eyes), and high myopia (58 eyes). Participants underwent comprehensive ophthalmological examinations, including intraocular pressure, axial length, cycloplegic refraction, lens morphology, accommodation measurements, and Brillouin optical scanning of the lens. Additionally, demographic information, such as age and sex, was recorded. Normality tests were performed on the data using the Kolmogorov-Smirnov test. Between-group differences were examined using the Kruskal-Wallis test. Correlation and multiple regression analyses were conducted to analyze the factors associated with lens biomechanical properties and accommodation. Results: The mean longitudinal modulus of the crystalline lens nucleus (LMN), anterior cortex (LMAC), and posterior cortex (LMPC) was 3.395 ± 0.027 GPa, 3.030 ± 0.066 GPa, and 2.990 ± 0.066 GPa, respectively, in adult myopia and 3.342 ± 0.024 GPa, 3.015 ± 0.0488 GPa, and 2.978 ± 0.049 GPa, respectively, in emmetropia. LMN was significantly higher in myopia (difference = 0.047, 95% confidence interval [CI] = 0.037 to 0.057, P < 0.001) and increased significantly with higher degrees of myopia (standardized β = -0.712, P < 0.001). No statistical differences in the LMAC or LMPC were observed between myopia and emmetropia. Lens densitometry on the centerline was the only lens parameter independently correlated with LMN (standardized β = -0.282, P < 0.01). Increased LMN in myopia was independently correlated with increased amplitude of accommodation (AMP) and decreased accommodative facility (AF; standardized β = 0.198, -0.237, all P < 0.05). Conclusions: LMN was significantly higher in adult patients with myopia than in emmetropia and increased with increasing myopia. Increased LMN in myopia significantly correlated with decreased AF and increased AMP. High LMN may be an important biological alteration during the development of adult myopia, especially high myopia, providing new insights into myopia pathogenesis.