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      Glaukos iStent ® Trabecular Micro-Bypass

      other
      Middle East African Journal of Ophthalmology
      Medknow Publications
      Intraocular pressure, glaucoma, iStent

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          Abstract

          The iStent trabecular micro-bypass system (Glaukos Corp. Laguna Hills, CA) was developed to address the limitations of current medical and surgical therapies for glaucoma treatment. The iStent ® is inserted ab interno through a small temporal clear corneal incision, bypassing the trabecular meshwork and placed in Schlemm's canal at the lower nasal quadrant. Implantation of this stent into Schlemm's canal allows aqueous humor to drain directly from the anterior chamber into Schlemm's canal bypassing the obstructed trabecular meshwork. For this review, a Medline search was performed using the terms “trabecular micro-bypass stent” and “trabecular bypass stent.” The online abstract database for the American Academy of Ophthalmology was also reviewed. Abstracts which duplicated published articles were excluded. All relevant papers (n is equal to three) and abstracts (n is equal to one) were included in this review. Multiple, prospective multi-country, clinical trials have demonstrated the safety and efficacy of iStent in reducing IOP, when compared to traditional treatment modalities, while reducing/ eliminating the need for ocular antihypertensive drugs when implanted in OAG patients during combined cataract surgery or in patients with glaucoma refractory to traditional treatment modalities.

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          Most cited references5

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          Outflow resistance of enucleated human eyes at two different perfusion pressures and different extents of trabeculotomy.

          Aqueous outflow resistance of enucleated human eyes was measured at 7 and 25 mm Hg before and after partial and complete (12 clock hours) internal trabeculotomy. Following complete trabeculotomy, 71% of the resistance was eliminated at 25 mm Hg while only 49% was eliminated at 7 mm Hg. In contrast to published findings in eyes with intact trabecular meshwork where the resistance increased with increasing IOP (1), following complete trabeculotomy, the resistance decreased 2% per mm Hg with increasing IOP. Experiments with trabeculotomy limited to part of the circumference showed that a one hour trabeculotomy produced 41% (25 mm Hg) to 60% (7 mm Hg) of the effect of a twelve hour trabeculotomy. The results indicate that a surprisingly high fraction of aqueous outflow resistance resides in the distal aspects of the outflow system at normal IOP, and that this distal resistance drops as IOP is increased.
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            Trabecular bypass stents decrease intraocular pressure in cultured human anterior segments.

            To determine the effect on intraocular pressure (IOP) of bypassing the trabecular meshwork in cultured human anterior segments. Prospective laboratory investigation using normal human eyes obtained at autopsy. Anterior segments from 21 eyes were placed in perfusion culture, and trabecular bypass stents were inserted through the trabecular meshwork, with the lumen of the tube opening into Schlemm's canal. Eyes received from one to four stents, placed equidistant apart. In eyes receiving one or two stents, additional stents were later added to a maximum of four per eye. Intraocular pressure was lowered after placement of a single stent, from 21.4 +/- 3.8 mm Hg to 12.4 +/- 4.2 (P < .001). This corresponded to an 84% increase in facility of outflow. Eyes receiving more than one stent had final IOP of 11.9 +/- 3.7 mm Hg. Nine eyes had sequential addition of stents, and seven of these had a further decrease of IOP (13.6 +/- 4.1 to 10.0 +/- 4.3; P = .02). Excision of the entire meshwork, between stents, dropped IOP to 6.3 +/- 3.2 mm Hg, indicating some residual meshwork or canal resistance remained even after placement of three stents. Bypass of the trabecular meshwork lowers IOP in cultured human anterior segments. One stent produced the greatest change in pressure. The sequential addition of more stents further lowered pressure in seven of nine eyes. This technique holds promise as a new clinical surgery for glaucoma.
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              Coexistent primary open-angle glaucoma and cataract: interim analysis of a trabecular micro-bypass stent and concurrent cataract surgery.

              To evaluate the safety and efficacy of the iStent Trabecular Micro-bypass Stent in patients undergoing concurrent cataract and glaucoma surgery. Prospective, 24-month, uncontrolled, multicenter, multicountry evaluation of 58 patients with uncontrolled primary open-angle glaucoma (including pseudoexfoliation and pigmentary) and cataract. Patients underwent clear cornea phacoemulsification followed by ab interno gonioscopically guided implantation of the iStent. Of the 48 per protocol population, 42 patients completed 12 months of the 24-month study, and their data are included in this interim analysis. At baseline, mean (+/-SD) intraocular pressure (IOP) was 21.7+/-3.98 mmHg. At 12 months, mean IOP was reduced to 17.4+/-2.99 mmHg, a mean IOP reduction of 4.4+/-4.54 mmHg (p<0.001, 18.3%). At baseline, patients were taking a mean 1.6+/-0.8 medications. By 12 months, the mean number of medications was reduced to 0.4+/-0.62 (p<0.001). Half the patients achieved an IOP < or =18 mmHg and were able to discontinue hypotensive medication by the 12-month visit. The most commonly reported device-related adverse events were the appearance of stent lumen obstruction (7 eyes) and stent malposition (6 eyes). None of the adverse events were deemed serious. In patients undergoing concurrent cataract and glaucoma surgery, the iStent was safe and efficacious for the reduction of IOP and medication therapy.
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                Author and article information

                Journal
                Middle East Afr J Ophthalmol
                MEAJO
                Middle East African Journal of Ophthalmology
                Medknow Publications (India )
                0974-9233
                0975-1599
                Jul-Sep 2009
                : 16
                : 3
                : 138-140
                Affiliations
                From the Laurel Eye Clinic, 50 Waterford Pike, Brookville, PA 15825
                Author notes
                Corresponding Author: Laurel Eye Clinic, 50 Waterford Pike, Brookville, PA 15825. E-mail: nichamin@ 123456laureleye.com
                Article
                MEAJO-16-138
                10.4103/0974-9233.56227
                2813604
                20142980
                baf90011-2a87-4b48-8cfd-09907ad62e16
                © Middle East African Journal of Ophthalmology

                This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                Categories
                Symposium - Glaucoma

                Ophthalmology & Optometry
                glaucoma,istent,intraocular pressure
                Ophthalmology & Optometry
                glaucoma, istent, intraocular pressure

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