[Morphometric OCT parameters of the lens under accommodative stimulus. Report 1. Assessment of age-related changes]

The structural approach to studying the mechanism of accommodation and its age-related changes focuses on analyzing morphometric parameters (size, shape, and position) of the crystalline lens as the key element responsible for changes in clinical refraction during accommodation. The latest-generation swept-source (SS) anterior segment optical coherence tomography (AS-OCT) device CASIA2 (Tomey, Japan) enables near-screening evaluation of lens shape and position both at baseline and under accommodative stimulus. In the latter case, the integrated optical system provides lens-induced accommodative stress directly in the examined eye.

This study aimed to evaluate age-related changes in various morphometric parameters of the lens measured by CASIA2 OCT under accommodative stimulus.

The study cohort comprised 74 healthy volunteers (123 eyes, i.e., clinical observations) aged 20-85 years. The exclusion criteria were clinically significant refractive errors and ocular diseases. Three groups were formed according to age: 20-30 years, 31-50 years, and >51 years (43, 33, and 47 clinical observations, respectively). Scanning was performed under conditions of relative accommodative rest and during accommodative stimulus. In the latter case, a lens-induced method of accommodative stimulus was used, employing a -5.0 D negative spherical lens and a fixation target in the form of a radial figure integrated into the optical system of the CASIA2 OCT device.

Analysis of the entire cohort (n=123) revealed significant changes in morphometric parameters of the lens under accommodative stimulus, including a decrease in the radius of curvature of the anterior (p=0.003) and posterior (p=0.045) lens surfaces, an increase in lens thickness (p=0.011) and nuclear thickness (p=0.007), as well as a reduction in lens diameter (p=0.026) and anterior chamber depth (p=0.033). The radius of curvature of the anterior lens surface under relative accommodative rest in Group 1 (20-30 years) was significantly higher (p=0.00) than in Groups 2 (31-50 years) and 3 (>51 years), with median values of 11.62, 9.47, and 9.25 mm, respectively. The magnitude of changes in lens curvature radius significantly decreased with increasing age for both the anterior and posterior surfaces. Baseline lens thickness and nuclear thickness increased significantly with age and also demonstrated an increase under accommodative stimulus across all age groups. A statistically significant correlation with age was found for the radius of curvature of the anterior surface (r=-0.371; p=0.00) and the posterior surface (r=-0.224; p=0.013), as well as for lens thickness (r=0.268; p=0.003).

Anterior segment OCT using the CASIA2 system is a highly informative method for assessing morphometric parameters of the crystalline lens under conditions of relative accommodative rest and lens-induced accommodative stress. Under accommodative stress, statistically significant changes included a decrease in the radius of curvature of the anterior and posterior lens surfaces, an increase in lens thickness and nuclear thickness, and a decrease in lens diameter and anterior chamber depth. Analysis of the magnitude of changes induced by accommodative stimulus and their correlation with age demonstrated statistically significant negative associations between age and the radius of curvature of the anterior and posterior lens surfaces, and a positive association with lens thickness.