Effect of suction angle on zonular fibers during residual cortex removal in phacoemulsification using finite element modeling

PURPOSE: To evaluate the effect of suction direction on zonular fibers' mechanical behavior using finite element modeling. SETTING: Laboratory study. DESIGN: 3D finite element model experimental study. METHODS: A 3D finite element model was developed, including nucleus covered by cortex and capsule. Similar to cataract surgery, a circular rapture was considered at the top of the capsule to apply suction pressure. Finally, zonular fibers were modeled as a continuum body using 3D solid elements (C3D8R). A custom FORTRAN subroutine was implemented to enforce tension-only behavior, mimicking the physiological characteristics of the zonular fibers, which are resistant to tensile but not compressive loads. This method allows for a realistic simulation of zonular mechanics during cortical aspiration. RESULTS: The suction processes in tangential and normal angles were simulated. The resulting relative displacements between the cortex and capsule, as a criterion of cortex separation, vs the resulting maximum zonule displacements, were recorded in each model. The cortex-capsule relative displacement vs maximum zonule displacement indicated a diagram slope of 0.09 for tangential applying pressure and 0.02 in the case of applying normal pressure. CONCLUSIONS: The results illustrated that zonular fibers were less tensile in a specific magnitude of cortex-capsule relative displacement under tangential applying pressure, which means that eye zonular fibers have a lower risk of failure until the separation of the lens cortex.