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Henrik Barth, Sven W Crafoord, Cyrille Vinchon, Sten Andreasson, Fredrik K Ghosh; A cross-linked hyaluronic acid hydrogel (Healaflow ®) as a potential vitreous substitute. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2338.
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Vitrectomy surgery mandates a way to substitute the natural vitreous and to tamponade any retinal breaks. The clinically available alternatives are still flawed with side effects such as inflammation, rise in intraocular pressure, cataract formation, and a need for head posturing. In this study, a hydrogel of cross-linked sodium hyaluronic acid (Healaflow®) is evaluated for use as a novel vitreous substitute utilizing an in vivo model.
A combined 25-20-gauge pars plana vitrectomy with posterior vitreous detachment was performed in the right eye of twelve pigmented rabbits, with subsequent injection of approximately 1 ml of Healaflow®. Clinical evaluation, intraocular pressure measurement and full-field ERG were performed postoperatively at intervals up to 105 days. The rabbits were sacrificed at different time-points between 42 and 105 days. After enucleation, the eyes were examined macroscopically, photographed, and prepared for histological examination with routine microscopy and immunohistochemical analyses.
The cross-linked sodium hyaluronic acid hydrogel was injected successfully and remained translucent but did not retain its structural integrity throughout the postoperative period of up to three months, although some viscous remnants were seen. One rabbit was lost due to unrelated causes. In two eyes iatrogenic partial retinal detachments were seen and in two eyes significant cataract were formed due to intraoperative complications. A slight postoperative rise in intraocular pressure was observed. ERG-recordings revealed no toxic effect on rod or cone function on follow up to three months. Microscopy and immunohistochemistry demonstrated normal morphology with some Müller cell activation (up-regulation of glial acidic fibrillary protein) compared to un-operated eyes and no significant DNA-fragmentation (TUNEL-assay).
A multitude of compounds have been investigated as candidates for vitreous substitution. To date, none of these compounds have been able to meet both physical demands and provide a good biocompatibility. Healaflow® did not affect retinal morphology or function negatively, making it highly interesting in this setting. The gel remained, and its viscous structure was maintained for at least a couple of weeks allowing for an effective tamponade. Future work will include an increased ratio of cross-linking to prolong gel structural integrity even further.
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