A Novel 8-mm Schlemm's Canal Scaffold Reduces Outflow Resistance in a Human Anterior Segment Perfusion Model

Abstract

PURPOSE.To study the effect on outflow facility and outflow resistance of a nitinol microstent implanted into Schlemm's canal.METHODS. Using a constant pressure perfusion method, outflow facility and outflow resistance were measured in 26 pairs of dissected anterior segments from donated human eyes. Measurements were made at perfusion pressures of 10, 20, 30 and 40 mm Hg. The Hydrus Microstent was placed in Schlemm's canal of one eye and the contralateral eye underwent a sham procedure. Outflow facility and outflow resistance were measured again after the microstent implantation or sham procedure.RESULTS. The Hydrus Microstent significantly increased outflow facility from 0.33 6 0.17 lL/min/mm Hg to 0.52 6 0.19 lL/ min/mm Hg (P < 0.001). Outflow resistance was significantly reduced from 4.38 6 3.03 mm Hg/lL/min at baseline to 2.34 6 1.04 mm Hg/lL/min (P < 0.001) with the microstent. There was a linear correlation between outflow resistance at baseline and decrease in outflow resistance with the microstent (R 2 ¼ 0.89, P < 0.0001).CONCLUSIONS. The increase in outflow facility and decrease in resistance supports the potential use of the Hydrus Microstent as a surgical option to reduce intraocular pressure (IOP). The IOP-lowering effect may be higher in eyes with higher outflow resistance (and IOP) as compared with eyes with lower outflow resistance (and IOP). (Invest Ophthalmol Vis Sci.

IOP Elevation Reduces Schlemm's Canal Cross-Sectional Area

“…While the present cause-and-effect relationship was IOP perturbation leading to morphometric response, the same relationship has been observed with a morphometric perturbation leading to IOP response. Gulati et al 22 implanted a scaffold in SC, inducing a large increase in SC-CSA. 22 This morphometric alteration resulted in a decrease in IOP.…”

“…Gulati et al 22 implanted a scaffold in SC, inducing a large increase in SC-CSA. 22 This morphometric alteration resulted in a decrease in IOP. The same concept may be applied to monitor the effects of minimally invasive nonpenetrating glaucoma procedures and implantation of devices designed to bypass the trabecular network.…”

A Randomized Trial of a Schlemm's Canal Microstent with Phacoemulsification for Reducing Intraocular Pressure in Open-Angle Glaucoma

“…23 Multiple laboratory studies examining the Hydrus Microstent using human cadaveric tissue in an anterior segment perfusion model have demonstrated an increase in outflow facility compared with untreated controls. 24,25 …”

Outflow Enhancement by Three Different ab Interno Trabeculectomy Procedures in a Porcine Anterior Segment Model

“…Since a low baseline IOP may lead to an insignificant IOP reduction, we also examined the IOP responses at a higher perfusion rate of 10 µl/min at the baseline and after the first and second TM removal processes. If any clear signs of leakage (IOP< 5 mmHg at the baseline), contamination or obstruction (IOP>50 mmHg at any point) were observed at any time during the process, the samples were removed from the experiment [20].…”