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A. S. Bansal, H. E. Grossniklaus, T. W. Olsen; A Porcine Model of Proliferative Vitreoretinopathy. Invest. Ophthalmol. Vis. Sci. 2010;51(13):6085.
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Proliferative vitreoretinopathy (PVR) is the principle cause for failed retinal detachment (RD) surgery. Frenzel et al. (IOVS 1998) developed a dispase-based model of experimental PVR in rabbits. The rabbit model has limitations. A large animal pig model of PVR has several advantages: 1) Larger eye that allows for surgical intervention, 2) a holangiotic retina, 3) has scleral anatomy similar to humans, 4) has an area centralis, 5) has a choroid-Bruch’s-retinal pigment epithelial complex similar to humans. The aim of our study is to develop a large animal model of PVR using dispase in pigs that allows for surgical manipulation and intervention that is not possible in other models.
We adapted the model of Frenzel et al. to the pig (n=10). The pigs weighed 10-15 Kg. All pigs were anesthetized prior to intervention. The first four received an intravitreal injection of dispase (0.3 units/0.3cc) and two received intravitreal saline (controls). None developed PVR or RD. Therefore, a ‘transequator’ group of four pigs were injected using a 25-guage sharp needle extending through the equator to the opposite equator in order to create a tear in the retina. Dispase (1.5 units/0.1cc) was injected as the needle was withdrawn. All animals were examined using indirect ophthalmoscopy and ultrasound at 1, 3, and 6 weeks post-injection. PVR was graded according to standard clinical definitions. All pigs were euthanized at 6 weeks and eyes were enucleated and examined histologically with H&E stain.
Three of four eyes injected intravitreally using 0.3 units/0.3cc dispase showed only vitreous haze and/or hemorrhage at 1 week. The vitreous and retina were normal in both saline control eyes. With the high-dose dispase, transequatorial injection, three of four eyes developed PVR at 6 weeks. One eye developed a classic PVR related RD, one eye had an open-anterior, closed posterior funnel RD, and one eye had surface fibrosis and no RD. Histopathology of the enucleated specimens confirmed the presence of PVR.
The porcine model using a transequatorial injection of high-dose dispase described represents a new model system to study surgical and pharmacotherapeutic intervention for PVR. This large animal model closely replicates the human condition.
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