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Nonlinear tissue processing in ophthalmic surgery
Published in Pablo Artal, Handbook of Visual Optics, 2017
If a large volume has to be addressed by the laser focus, it is much easier to realize this with optics of lower numerical aperture (Figure 16.8). Accordingly the cutting precision will decrease, which is acceptable for cataract surgery, not only for lens fragmentation but also for capsulorhexis and corneal incisions. However, this would be not acceptable for corneal refractive surgery.
Numerical modelling to assess the tear force of human capsulotomy margin
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
The FE model of the lens capsule was established to overcome the limitation of the quantitative analysis of the tear force. From the matched simulated tearing force with the values of the experimental tear force, our model was effectively validated to simulate the dynamic tearing response process. However, there are some incomplete places. The capsule will collapse if the tissue wrapped by the capsule is removed after capsulorhexis, and it’s nearly impossible to achieve a perfectly circular and centered rim during surgery. The capsule was considered as a bilinear elastic material, while the capsule has the nonlinear characteristics. In addition, the thickness of the capsule was nonuniform in different region. To simplify the model, thickness was set to be the same at different regions.
A review of haptic simulator for oral and maxillofacial surgery based on virtual reality
Published in Expert Review of Medical Devices, 2018
Similar to cutting, tearing is performed by breaking connections between neighbors within volumetric models [73]. However, these broken connections are determined by tension and shearing between two stretched primitives in tearing rather than by cutting path and applied force in cutting. Tearing simulation has been realized in many surgery simulators. For example, capsulorhexis simulation has been widely used in cataract surgery simulators [74,75]. Mucosal tearing has been integrated into some OMFS simulators [27]. However, incision is hard for prediction due to the constraint of complicated biomaterials. Some research groups have been working on tearing simulation. Most of them followed a similar approach used in virtual cutting algorithms, reducing the computational cost to some degree. Payandeh et al. [76] defined two types of tearing, i.e. tear-into and tear-through, and realized the tearing simulation of mesh models through subdividing surfaces and using groove polygons to connect them. Cotin et al. [77] explored several performances of models based on linear elasticity theory and finite-element modeling in complex anatomy simulation and found that the hybrid elastic model was suitable for cutting and tearing simulation.