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J.L. Ferreira, F. Vegini, C.R. Maliska; Use of Buoyancy Force in Replacing Dislocated Intraocular Lenses in the Vitreous . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3040.
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Purpose: The management of patients with displacement of the intra-ocular lens (IOL) vary according to the surgeon's preference. Replacement of the IOL using capsular support is preferred. Perfluorocarbone liquids (PFCLs) are used in conjunction with vitrectomy for protection of the retina and replacement of the IOL in these cases. A mathematical model to study the IOL movement in PFCLs liquids for using the buoyancy force as a new strategy for replacing the posteriorly dislocated IOL is proposed. Methods: A mathematical model was developed in order to study the fluid dynamics of IOL buoyancy movements in the vitreous cavity filled with PFCL. The IOL is manipulated by two Sinskey hooks, shifted to the vertical position and pushed down 5 mm approximately, facilitating its replacement by the buoyancy forces. This model assumes IOL’s movement from rest and in the vertical position, close to the ruptured posterior capsule. The viability of using the buoyancy forces in the replacement of two types of IOL [acrylic and polimetilmetacrilate (PMMA)] in two different PFCLs (perfluoroctane and perfluorodecaline) filling the vitreous was studied. The following data was used: specific mass of the IOLs and of the PFCLs, volume and diameter of the optic and haptic portions of the IOLs, and the kinematic viscosity of the PFCLs. Results: Considering the speed and the kinetic energy of the IOLs, the PMMA IOL immersed in Perfluoroctane reaches the highest velocity. The PMMA IOL presents a bigger volume and a smaller density than the acrylic one, whith greater performance considering the buoyancy forces. Considering the PFCLs, perfluorodecalin density and kinematic viscosity are larger than the perfluoroctane, with better performance of the IOLs in perfluoroctane. When one considers the maximum distance of 5 mm into the eye, the physical properties of the IOLs and PFCLs have no significant difference, and either combination can be used in the surgery. Conclusions: The buoyancy force is an effective tool and can be safely used in repositioning a dislocated IOL in selected cases. The kinetic energy developed by the PMMA is larger than the acrylic IOL because the first one has a larger volume and a smaller density. The IOLs in perfluoroctane show larger kinetic energy than in perfluorodecaline because the last one has larger density mass and kinematic viscosity. When one considers the anatomy of the eye, the physical properties of the IOLs and PFCLs have no significant difference and either combination can be used in surgery.
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