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E.C. Kim, C.R. Bernardino, A.M. Fay, P.A. Rubin; Study of the Expansile Properties of a Hydrogel Implant Within Porcine Scleral Shells . Invest. Ophthalmol. Vis. Sci. 2003;44(13):664.
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Purpose: Hydrogel (Methylmethacrylate and N-Vinylpyrrolidone) is a biocompatible, expansile material used in scleral buckles and orbital expanders. This study investigates the expansile properties of a dehydrated, spherical hydrogel implant in an ex-corporis porcine evisceration model. Methods: Globe volume, coronal, axial, sagital diameters of 6 fresh, porcine eyes were measured. An evisceration was performed on each eye. The corneal button & the intraocular contents were removed, leaving a bare scleral shell. To mimic routine evisceration practices, a posterior sclerotomy was created over the optic nerve with a 7 mm corneal trephine (max allowed for dehydrated implant) in 3/6 globes(grp 2). The other 3 globes were left intact (grp 1). An 8 mm hydrogel sphere (IOP, Inc., Costa Mesa, CA) expands to a max of 20 mm in saline without counter-pressure. However expansion halts at a counter-pressure of 30 mmHg. An implant was placed within a scleral shell & the opening sutured in an interrupted horizontal mattress fashion with 5-0 polyglactin with overlapping scleral flaps. Globe volume & dimensions were measured at T=0, 1, 12, 24, 36 hr after being submerged in 20 ml of saline in individual containers at 20°C. Results: Pre-evisceration mean volume of 6.1 ml & mean dimensions of 22.5 x 22.0 x 20.7 mm were found. Table 1 contains globe dimensions & volume with time. By 24 hrs, the implant was almost completely expanded within the scleral shells of grp 2. There was no implant protrusion through sclerotomies & all maintained a spherical shape. There were no wound dehiscences. Conclusions: All spheres increased volume over the first 24 hrs. All wounds remained intact despite expansion of the implant. Volume increase was more rapid in grp 2 due to the posterior sclerotomy allowing saline to directly hydrate the hydrogel. In-vivo use of this implant with increased temperature, blood flow, and transudation may allow for more rapid expansion. Though there was no protrusion of the implant through the sclerotomy, protrusion of the implant may be advantageous by increasing the volume of the implant. Implants of larger diameter with less expansile properties should be tested for this effect. Globe dimensions (mm) & vol (ml) with time (hr) View OriginalDownload SlideView OriginalDownload Slide
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