Morphometric OCT parameters of the lens under accommodative stimulus. Report 2. Pilot study of the relationship between changes in the curvature of the anterior lens surface and the biomechanics of the anterior capsule

Introduction. The ability of the crystalline lens to change its shape is a key component of accommodation. As part of the lenticular theory of presbyopia, involutional changes in the lens substance itself are considered to be of primary importance. At the same time, the role of the capsule, which essentially serves as a structural, shape-modifying “framework” for the lens substance, remains insufficiently studied. Accordingly, one approach to clarification of the pathogenesis of presbyopia may involve investigating the relationship between potential changes in lens shape during accommodation and the biomechanical properties of its capsule. Purpose. This study aimed to assess the potential relationship between accommodative stimulus-induced changes in the curvature of the anterior lens surface and the biomechanical parameters of the anterior capsule based on sequential clinical and experimental analysis. Material and methods. The study was conducted in a group of 11 patients (11 eyes, i.e., clinical observations) of presbyopic age scheduled for and undergoing standard phacoemulsification with intraocular lens implantation for uncomplicated cataract. Prior to surgery, the radius of curvature of the anterior lens surface was measured at baseline and under accommodative stimulus using the CASIA2 device (Tomey, Japan). Anterior lens capsule specimens with a diameter of 4.0—5.5 mm were obtained during surgery after continuous curvilinear capsulorhexis. The elastic modulus (Young’s modulus) of the specimens was determined using atomic force microscopy. Results. Correlation analysis involved the use of an integral parameter — the magnitude of change in the radius of curvature of the anterior lens surface induced by accommodative stimulus. A pronounced moderate positive correlation was identified between changes in the radius of curvature of the anterior lens surface and the elastic moduli of the outer and inner surfaces of the anterior capsule (r=0.560 and r=0.603, respectively). However, this relationship was statistically significant only for the inner surface of the capsule but not for the outer surface (p=0.050 and p=0.073, respectively). Conclusion. This is the first study investigating the potential relationship between changes in the curvature of the anterior lens surface and the biomechanical properties of the anterior capsule using the same study object, which enabled sequential clinical (morphometric) and experimental (biomechanical) analyses. Based on the obtained results, age-related changes in the biomechanical properties of the lens capsule may be considered one of the factors within the lenticular theory of presbyopia development.