Haptic Deformation Research Articles

Evaluation of Flanged Haptics Intrascleral Sutureless Intraocular Lens Fixation

Background: successful intraocular lens (IOL) placement in patients undergoing cataract surgery has become synonymous with the IOL being placed in the capsular bag. Purpose: to evaluate the flanged haptic sutureless intrascleral intraocular lens fixation with double needle technique as a method of scleral fixation of posterior chamber IOL (PCIOL) as regard to its stability and safety as well as its complications. Patients and Methods: this is a prospective study, which included 20 eyes of 20 patients with aphakia with no adequate capsular support. Results: post-operatively the best corrected visual acuity (BCVA) was improved to reach up to 0.8 decimal unit. Intra-operatively, haptic breakage was reported in 3 cases where the IOLs were explanted and new IOLs were implanted and sclerally fixated. The post-operative complications included iris capture in 2 cases (10%), haptic deformation in 2 cases (10%), exposure in 5 cases (25%) and slippage in 2 cases (10%), corneal edema in 6 cases (30%), IOL decentration in 4 cases (20%) one of them was significantly decentered and needed for reoperation where one point fixation by a stitch of the slipped haptic , spontaneous IOL dislocation in 2 cases (10%) 1 month and 3 months post-operatively, both required re operation where the slipped IOL was explanted and new one is re implanted and sclerally fixated. There were no incidents of post-operative ciliary body injury, retinal tear or detachment or endophthalmitis. Conclusions: the flanged haptics intrascleral sutureless IOL fixation with double needle technique can be done for aphakic cases with no adequate capsular support.

Nonlinear viscoelastic contact and deformation of freeform virtual surfaces

This article is concerned with the haptic deformation display of discrete viscoelastic surfaces by means of a human fingertip. The virtual surface of a deformable quadrilateral mesh is interactively deformed by a Kelvin–Voigt soft fingertip model attached to the end-effector of a haptic interface device. In achieving this task, a nonlinear constitutive model approximating experimental data from literature is developed for determining the contact point deformations. By employing a new kernel weighting function, the deformations are distributed dependently on the discrete surface topology based on a nonlinear spring–damper net around the contact location. For illustration and evaluation of the proposed approach, a parallel robotic device with a constraint-based controller is adopted. The grip of the device is moved by the user to feel a sense of touch as the soft fingertip deforms the mesh surface of an ex vivo porcine liver tissue. Experimental data indicates stable realistic interactions thorough mechanical coupling between the soft fingertip and the deforming liver tissue. Dynamic response data of liver show rate-dependent hysteretic deformations and match closely with experimental indentation data from literature. A thorough analysis of mesh node count on the sample rate and the rendering quality is also presented.

Frictional Compliant Haptic Contact and Deformation of Soft Objects

This paper is concerned with compliant haptic contact and deformation of soft objects. A human soft fingertip model is considered to act as the haptic interface and is brought into contact with and deforms a discrete surface. A nonlinear constitutive law is developed in predicting normal forces and, for the haptic display of surface texture, motions along the surface are also resisted at various rates by accounting for dynamic Lund-Grenoble (LuGre) frictional forces. For the soft fingertip to apply forces over an area larger than a point, normal and frictional forces are distributed around the soft fingertip contact location on the deforming surface. The distribution is realized based on a kernel smoothing function and by a nonlinear spring-damper net around the contact point. Experiments conducted demonstrate the accuracy and effectiveness of our approach in real-time haptic rendering of a kidney surface. The resistive (interaction) forces are applied at the user fingertip bone edge. A 3-DoF parallel robotic manipulator equipped with a constraint based controller is used for the implementation. By rendering forces both in lateral and normal directions, the designed haptic interface system allows the user to realistically feel both the geometrical and mechanical (nonlinear) properties of the deforming kidney.

Outcomes of glued foldable intraocular lens implantation in eyes with preexisting complications and combined surgical procedures

To evaluate the visual outcomes and complications of glued foldable intraocular lens (IOL) implantation in patients with a wide range of ocular pathologies and/or having combined surgical procedures. New York Eye and Ear Infirmary of Mount Sinai, New York, New York, USA. Retrospective case series. A chart review was conducted of all glued foldable IOL procedures performed in eyes with absent or insufficient capsule support. Patients with a postoperative follow-up less than 3 months were excluded from analysis. Intraoperative and postoperative complications, the postoperative course, and visual and refractive outcomes were analyzed. Sixty-five eyes (64 patients) were evaluated over a mean follow-up of 9.1 months ± 6.2 (SD). Ocular comorbidities were present in 98.5% of eyes, and 95.4% had additional concurrent surgical procedures. There was a statistically significant improvement in corrected distance visual acuity (P = .046), with 89.2% of eyes achieving better or equal vision postoperatively. Intraoperative complications included ocular hemorrhage (10.8%), haptic deformation (10.8%), and haptic breakage (1.5%). Postoperative complications included elevated intraocular pressure (13.8%), optic capture (12.3%), persistent anterior chamber inflammation (6.2%), IOL tilt (4.6%), cystoid macular edema (3.1%), recurrent ocular hemorrhage (3.1%), and retinal detachment (1.5%). The glued foldable IOL technique resulted in favorable visual outcomes but with a moderate risk for IOL-related and other postoperative complications in eyes with complex ocular comorbidities having combined surgical procedures. No author has a financial or proprietary interest in any material or method mentioned.

Layered rhombus-chain-connected model for real-time haptic rendering

The modeling and simulation of deformable objects is a challenging topic in the field of haptic rendering between human and virtual environment. In this paper, a novel and efficient layered rhombus-chain-connected haptic deformation model based on physics is proposed for an excellent haptic rendering. During the modeling, the accumulation of relative displacements in each chain structure unit in each layer is equal to the deformation on the virtual object surface, and the resultant force of corresponding springs is equivalent to the external force. The layered rhombus-chain-connected model is convenient and fast to calculate, and can satisfy real-time requirement due to its simplicity. Experimental study in both homogenous and non-homogenous virtual human liver and lungs based on the proposed model are conducted, and the results demonstrate that our model provides stable and realistic haptic feeling in real time. Meanwhile, the display result is vivid.

Haptic Interaction with Elastic Volumetric Structures

Considerable efforts have been done to produce realistic results when simulating interaction with elastic materials. Many applications such as surgery planning, medical training, or virtual sculpting would benefit from a plausible simulation scenario. However, even though many works have proposed very satisfactory results, realistic simulation of deformable bodies is still an open issue. One of the challenges when designing a realistic elastic body simulation is the huge amount of data that needs to be processed. For the inner properties of the material are crucial when it comes to reproduce the elastic problem, the simulation naturally calls for volumetric information. In this paper the authors propose a technique to interactively deform 3D images, such as those acquired by a CT scanner. While producing a physically plausible haptic feedback, deformation and visualization algorithms produce an efficient and natural feeling. Using a free form deformation structure as a wrapper, it is possible to deform complex structures at high frame rates, independently of the size of the volume.

Area Based Adaptive Subdivision of a Triangular Mesh for Visio Haptic Deformation

Area Based Adaptive Subdivision of a Triangular Mesh for Visio Haptic Deformation

A Novel Haptic Deformation Modelling Method using Spherical Harmonic Representation and Radial Basis Function Neural Network

In the haptic modelling of deformable soft objects in virtual reality, due to the complicated relationship between the deformation and the applied force, it is a challenging task to achieve the balance between accuracy and efficiency. In this paper, a novel approach based on spherical harmonic (SH) representation and Radial Basis Function neural network(RBF-NN) to simulating the virtual deformation of soft objects was proposed. The object surface was represented by SH, which features of orthonormality, rotational invariance, and multi-resolution. Given the density, Young's modulus, Poisson ratio of the object and interactive position of the applied force, the haptic deformation model was estimated by a Radial Basis Function (RBF) based neural network model, which was trained with Least Error Measure method. The simulation results indicated that the haptic deformation model could be accurately calculated using the proposed approach and the computational time was acceptable for real-time applications.

Capsule contraction syndrome with haptic deformation and flexion

We report a case series of capsule contraction syndrome in 5 eyes of 4 patients and describe a previously unreported complication: full flexion of the haptics onto the anterior surface of the optic. Haptics have been reported to slide anterior to the optic while remaining in their original coronal plane. As surgeons move to the use of preloaded injectable IOLs, it is important to scrutinize haptic-optic junction design and IOL material in the light of this complication.

Interactive soft‐touch dynamic deformations

AbstractIt is crucial for the users to touch, grasp and manipulate the interested objects through our sense of touch in many interactive applications, such as on‐line computer games, interactive cartoon design, and virtual prototyping. In this paper, we propose an interactive haptic deformation approach which incorporates the dynamic simulation of mass–spring systems and flexible control of free‐form deformation in the touch‐enabled soft‐object deformation. Through distributing mass, spring and damping coefficients of the object to the bounded Bezier volume lattice, the deformation of the object related to the haptic avatar follows the physical laws and has high working rate. Both homogenous and inhomogenous materials are simulated. The anchor nodes of haptic input are specified to create amazing special effects during the interactive haptic deformation. Interactive haptic deformations of three‐type tropic fishes, Angel, Demekin, and GuppyBlueGrass, have been experimented to simulate vivid fish swimming processes in the virtual ocean scene. Our proposed approach provides touch‐enabled input and efficient performance in the flexible deforming controls, letting the objects move in a dynamic, cartoon‐style deforming manner. Copyright © 2007 John Wiley & Sons, Ltd.

Clinical effects of primary posterior continuous curvilinear capsulorhexis in eyes with single-piece hydrophilic acrylic intraocular lenses with and without haptic angulation

To evaluate the clinical effects of a primary posterior continuous curvilinear capsulorhexis (PCCC) on the intraocular performance of hydrophilic acrylic single-piece intraocular lenses (IOLs) with and without haptic angulation. Department of Ophthalmology, Medical University of Vienna, Vienna, Austria. A prospective study comprised 52 patients with bilateral age-related cataract who had standard cataract surgery including a PCCC. One eye of each patient was randomized to receive a hydrophilic acrylic IOL with haptic angulation (ACR6D SE, Laboratoires Cornéal) and the contralateral eye, a hydrophilic acrylic IOL without haptic angulation (C-flex 570C, Rayner). The following parameters were assessed: regeneratory posterior opacification (RPO) in the central, intermediate, and peripheral areas (scale 0 to 10); anterior capsule opacification (ACO); best corrected visual acuity (BCVA); and contrast sensitivity (CSF). Thirty-one patients completed the 1(1/2)-year follow-up. In both IOL groups, RPO within the PCCC was slight in the central area, with a mean score of 0.33 +/- 0.84 (SD) in the angulated IOL group and 0.16 +/- 0.57 in the nonangulated IOL group (P = .29). The mean RPO score in the peripheral area was 2.07 +/- 1.37 and 2.35 +/- 1.45, respectively (P = .12). The difference between the central and peripheral areas was 1.74 in the angulated IOL group (P<.00001) and 2.19 in the nonangulated IOL group (P<.00001). Haptic deformation occurred in 9 eyes (29%) with an angulated IOL and no eye with a nonangulated IOL. There was significantly more ACO in the nonangulated IOL group (P = .012). There were no significant differences in BCVA or CSF between the 2 groups. Creating a PCCC led to significantly lower RPO intensity within the PCCC area than in the peripheral area in eyes with hydrophilic acrylic IOLs with and without haptic angulation. Haptic angulation had no apparent significant influence on the intensity of RPO or on BCVA and CSF. Haptic deformation may occur in hydrophilic IOLs with angulated haptics.

Elastodynamic shape modeler: a tool for defining the deformation behavior of virtual tissues.

A main goal of surgical simulators is the creation of virtual training environments for prospective surgeons. Thus, students can rehearse the various steps of surgical procedures on a computer system without any risk to the patient. One main condition for realistic training is the simulated interaction with virtual medical devices, such as endoscopic instruments. In particular, the virtual deformation and transection of tissues are important. For this application, a neuro-fuzzy model has been developed, which allows the description of the visual and haptic deformation behavior of the simulated tissue by means of expert knowledge in the form of medical terms. Pathologic conditions affecting the visual and haptic tissue response can be easily changed by a medical specialist without mathematical knowledge. By using the personal computer-based program Elastodynamic Shape Modeler, these conditions can be adjusted via a graphical user interface. With a force feedback device, which is similar to a real laparoscopic instrument, virtual deformations can be performed and the resulting haptic feedback can be felt. Thus, use of neuro-fuzzy technologies for the definition and calculation of virtual deformations seems applicable to the simulation of surgical interventions in virtual environments.

Clinical evaluation of the Unfolder

Purpose: To evaluate the clinical acceptability of the Unfolder™ for implantation of AMO® PhacoFlex II® (model SI-30NB or SI-40NB) intraocular lenses (IOLs).Setting: Six investigational sites in five states in the United States: Utah, Texas, Missouri, Minnesota, and Massachusetts.Methods: One hundred one patients from six investigational sites had implantation of an SI-30NB or SI-40NB IOL. Investigators evaluated the clinical acceptability of the Unfolder by comparing their experience with the injector with that using other implantation systems. Internal incision size (dimensions) was measured three times during surgery using a calibrated instrument. Data on safety and efficacy were collected.Results: The investigators rated the Unfolder as clinically acceptable. Mean internal incision size after phacoemulsification but before IOL implantation was 3.0 mm ± 0.1 (SD) (range 2.7 to 3.2 mm). Average internal incision size after IOL implantation was 3.1 ± 0.1 mm. There were no reports of haptic deformation, lens optic damage, or postoperative complications related to the Unfolder. No adverse events were reported.Conclusions: Investigators found the Unfolder easy to use. It provided controlled lens implantation through incisions 2.7 to 3.2 mm, with post-IOL implantation incisions ranging from 2.9 to 3.3 mm.

Measurement of elastic resisting forces of intraocular haptic loops of varying geometrical designs and material composition

The relationship between experimentally induced intraocular lens (IOL) haptic deformation and resulting elastic haptic counter-resisting forces measured by electronic dynamometry was examined for 34 different IOL haptics of varying material composition and geometrical designs. Poly(methyl methacrylate) (PMMA) and polypropylene loops of similar geometry did not fundamentally differ from one another, although lenses of differing geometry behaved differently. Unlike PMMA and polypropylene loops, soft haptics of poly-HEMA and silicone rubber demonstrated a larger elastic resistance force to the same degree of deformation. This was based upon design characteristics of the lenses and not upon intrinsic properties of the materials, which would have produced the opposite result. By comparative analysis of these dynamometer measurements and considerations of the lens design and elastic properties (including memory) of the component materials, we can calculate the stresses upon the zonular and capsular bag structures during and after IOL implantation.