Examining the effect of cortex suction angle in cataract surgery on the risk of zonules failure using finite element analysis
Seyed Hashem Daryabari1 *
- Assistant Prof. of Ophthalmology, Chemical Injury Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran
Abstract: The suction of the eye lens cortex is an integral step of cataract surgery, which induces tensile forces or even failure in lens zonules, especially in old populations with zonules poor mechanical strength. Two conventional angles of cortex removal, including suction in the tangential or normal direction to the cortex surface, have different resulting stress and the risk of failure. However, there is no study about the effect of suction angle on the risk of zonules failure. So, this investigation aimed to simulate lens cortex removal and evaluate the effect of suction direction on zonules' mechanical behavior using finite element modeling.
Methods: A 3D finite element model was developed, including an elastic nucleus covered by an elastoplastic cortex and a covering elastic capsule. Similar to cataract surgery, a circular rapture was considered at the top of the capsule to apply suction pressure. Frictional contacts were also defined to simulate the mechanical interactions between contacting parts. Finally, Zonules were modeled as 2-node elastic spring elements, connected around the capsule surface on one side and fixed to the inner lens surface on the other
Results: The suction processes in tangential and normal angles were simulated, and the resulting relative displacements between the cortex and capsule, as a criterion of cortex separation, versus the resulting maximum zonule displacements, were recorded in each model. The cortex-capsule relative displacement versus maximum zonule displacement indicated a diagram slope of 0.09 for tangential applying pressure and 0.02 in the case of applying normal pressure.
Conclusion: To conclude, the results illustrated that zonules were less tensile in a specific magnitude of cortex-capsule relative displacement under tangential applying pressure, which means eye zonules have a lower risk of failure until the separation of the lens cortex. However, the following investigations should consider the variety of material properties in different cases.
