Towards understanding the aetiology of high myopic strabismus using mechanical analysis and finite element modelling

It has been widely accepted that the pathology of high myopic esotropia, a special form of strabismus, is still not fully understood. In this study, the mechanical analysis and finite element analysis (FEA) of the oculomotor system was based on clinical MRI data and applied to examine the physiological hypotheses of extra-ocular muscle obliquity and deformation respectively. Our mechanical analysis indicated that the muscular obliquity is not the dominated cause of high myopic strabismus. Next, by simulating the effect of different forces applied to the cross section of each extra-ocular rectus muscles, the corresponding eyeball rotations were quantified on normal eyes, and high myopic eyes with and without strabismus. The model suggests that the limitation of rotation in high myopic strabismic eyes is mainly caused by the extra-ocular muscle deformation instead of, but related with, its obliquity, providing a better understanding of the aetiology of high myopic strabismus. To the best of our knowledge, this is the first mechanical and FEA model developed from clinical data to investigate the aetiology of high myopic strabismus, providing important tools for future studies.