Changes in Dimensions and Functions of Crystalline Lens in High Myopia Using CASIA2 Optical Coherence Tomography

Crystalline lens is the major dioptric component and varies with refractive status. In this study, we aim to evaluate the changes of dimensions and functions of crystalline lens in high myopia (HM) and its correlated variables using CASIA2 swept-source optical coherence tomography.

One hundred and thirty eligible eyes of myopic patients from 18 to 40 years old were enrolled and divided into low-to-moderate myopia (LMM) and HM groups according to spherical equivalent (SE). Anterior segment features, including lens thickness (LT), anterior radius of curvature (ARC), posterior radius of curvature (PRC), anterior chamber depth (ACD), and lens tilt were obtained by CASIA2. Lens power was calculated using Bennett's formula. Sixty-seven participants were imaged at the static state and the accommodative state induced by -3 diopter (D) stimulus.

Compared to the LMM group, the HM group exhibited a significantly reduction in LT, ARC, and lens tilt (all p < 0.01). Each parameter correlated positively with SE (all p < 0.01). Lens power increased with LT and tilt (r = 0.42, 0.45) but decreased with ARC and axial length (AL) (r = -0.37, -0.62) among highly myopic eyes. Multivariate regression analysis revealed that lower lens power appeared to be independently associated with axial elongation in both groups (LMM: β = -1.124, p = 0.002; HM: β = -1.603, p < 0.001, respectively). Decreases in ARC and ACD were accompanied by accommodative response in each group, while PRC reduced during accommodation (p = 0.009) only in HM.

Young adults with HM presented a thinner thickness, smaller tilt, less lens power, and higher accommodative response. Lens shape was closely associated with SE; however, AL was a meaningful indicator of lens power.