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L. Katz; From Theory to the Clinic: Exploiting Schlemm’s Canal . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1880.
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To determine if creating a patent bypass into Schlemm’s canal may restore fully functional physiologic outflow in patients with open–angle glaucoma (OAG) and significantly reduce IOP. Theoretical, in vitro, and clinical data are presented.
Evaluation of published and presented reports.
A fluid mechanics model was developed that found that a trabecular patent bypass in healthy eyes increased the facility of outflow by 13% and 26% with unidirectional and bidirectional flow, respectively. A study evaluating outflow facility in cultured human anterior segments perfusion model was also conducted. Eyes received between one and four stents, placed equidistant apart. IOP was lowered with 1 stent, from 21.4 mm Hg to 12.4 mm Hg (P < .001). Implantation of additional stents resulted in further IOP reductions and increases in facility–of–outflow. In a clinical evaluation, 47 patients with OAG and cataract underwent clear cornea phacoemulsification cataract extraction with ab–interno gonioscopically guided implantation of the iStentTM into Schlemm’s canal. The iStentTM is designed to create a patent bypass channel through the trabecular meshwork. The device extends slightly into the anterior chamber to allow the aqueous to exit. The fluid then flows through the stent into Schlemm’s canal. At baseline, mean (± SD) IOP was 21.5 (± 3.7) mm Hg. Six months after implantation of the iStentTM, the mean IOP was 15.8 (± 3.0) mm Hg, a mean IOP reduction of 5.7 (± 3.8) mm Hg (25%, P<0.001). Patient drug burden was decreased by a mean of 1.0 (± 0.8) medication.
Theoretical data has been validated in the lab and in the clinic. Re–establishing physiologic outflow by creating a patent bypass channel into Schlemm’s canal can provide substantial reductions in IOP and drug burden in OAG patients and trabecular bypass into Schlemm’s canal is a promising treatment for glaucoma. Additional research into fully exploiting circumferential flow within Schlemm’s canal is ongoing.
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