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Hady Saheb, Ian Grierson, Malik Y. Kahook, Murray A. Johnstone, Carol B. Toris, Iqbal I. Ahmed; In Vivo Biocompatibility Evaluation of a Novel Nickel-Titanium Schlemm's Canal Scaffold. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3749.
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© ARVO (1962-2015); The Authors (2016-present)
A new implant (Hydrus™ Aqueous Implant, Ivantis, Inc.) made of Nitinol (nickel-titanium alloy) that improves aqueous humor flow from the anterior chamber through Schlemm’s canal was implanted into rabbits and nonhuman primates (NHPs) to assess the local tissue biocompatibility.
New Zealand white rabbits were selected to evaluate the ocular biocompatibility of the Hydrus Aqueous Implant. Eight rabbits received implants inserted through the anterior chamber, into the sclera and subconjunctival space. The fellow eye underwent a sham procedure without implant. The rabbits were sacrificed after 6 months, and the eyes were examined by light microscopy. To assess the tissue response to the implant in Schlemm’s canal, Hydrus Implants were surgically inserted into Schlemm's canal of two NHPs, and the third served as a surgical sham control. After 13 weeks the animals were sacrificed, and the eyes were examined by light and scanning electron microscopy (SEM). The histological slides were evaluated by two independent assessors who were masked as to which eye had received the implant. The protocol was reviewed and approved by Xenometric’s Institutional Animal Care and Use Committee.
Minimal mononuclear cell infiltration and minimal fibrotic response at the site of the implants were observed in the rabbit eyes. Histological and SEM analysis of the NHPs demonstrated that the implants were located in Schlemm's canal. There was no evidence of an acute or chronic inflammatory response, granulation response or fibrosis in the outflow system or in adjacent tissues. There were minimal differences between study and control eyes. Although, rabbits are prone to inflammation, the response was limited and present in both the Hydrus implanted and sham operation eyes. In NHPs, there was only evidence of tissue reaction to mechanical distortion and no persistent inflammatory change or foreign body reaction.
The Hydrus Aqueous Implant was associated with minimal inflammation in both rabbit and NHP eyes with extended follow-up. In NHP eyes, the implant was placed within Schlemm's canal with a benign host response. It appears from these preclinical studies that the Hydrus Implant is biocompatible.
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