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Haiyan Gong, Elliot D. Cha, Varun Gorantla, Vikas Gulati, Shan Fan, Cassandra Steiner, Carol B. Toris; Characterization of Aqueous Humor Outflow through Novel Glaucoma Devices - A Tracer Study. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3743.
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© ARVO (1962-2015); The Authors (2016-present)
The mechanisms by which two novel glaucoma devices increase outflow facility in an ex vivo model of perfused human anterior segments were investigated and compared.
Methods: Pairs of human eyes with no history of ocular diseases or surgeries were obtained from several eye banks within 48 hours of death. Outflow facility (C) was measured at baseline and after implanting an 8mm intracanalicular scaffold, (HydrusTM Aqueous Implant, Ivantis, Irvine, CA) in Schlemm’s canal (SC) of each pair (N=11). The contralateral eye was either not implanted (controls, N=6) or with two trabecular micro-bypass stents in SC (iStent®, Glaukos, Laguna Hills, CA; N=5). A fixed volume of fluorescent tracer (FT) microspheres (200nm, 0.002%, 0.3 ml) was then perfused into the anterior chamber of each eye at 23 mmHg. Perfusate was collected from 8 pairs of eyes and the eyes were fixed. Anterior and posterior global images and confocal images were taken and examined. Fluorescence intensity was measured and areas with and without flow were analyzed. Paired and unpaired two-tailed t-tests were used for statistical analyses.
Compared to baseline, C increased significantly in both the Hydrus group (77%, p=0.04) and the two iStent group (55%, p= 0.049), whereas C did not change significantly in controls. Outflow patterns were segmental in control eyes. The Hydrus Implant group showed more tracer in the scleral veins and perfusate than controls and the two iStent group. Additionally, Hydrus Implant group showed less tracer in the trabecular meshwork than controls and the two iStent group. The confocal images show substantial dilation of SC in the quadrant of the Hydrus Implant and less dilation in the focal location of the iStents implants.
The Hydrus Aqueous Implant significantly increased outflow facility by increasing the total area involved in aqueous humor outflow. More scleral veins were accessed by the intracanalicular scaffold via multiple collector channels compared to controls or two iStent Implants.
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