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      Evaluation of Bleb Characteristics after Trabeculectomy and Glaucoma Implant Surgery in the Rabbit

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          The characteristics of the conjunctival bleb are some of the most important factors for the surgical success of glaucoma filtering surgery. To improve surgical outcome, we investigated bleb histology after 3 different glaucoma surgeries. Surgery was performed in 21 white rabbits. Rabbits were randomized to trabeculectomy or implantation with EX-PRESS or a silicone tube (each n = 7). Bleb survival, intraocular pressure (IOP), and vascularity were evaluated. At 6 weeks, eyes were enucleated for histological analysis. Postoperative IOP at 2 weeks was significantly lower in the trabeculectomy and the EX-PRESS group than in the silicone tube group ( p = 0.037) but not thereafter. Postoperative bleb survival ( p = 0.542) and vascularity ( p = 0.988) were similar among the 3 groups. Histologically, a capsule showing mild fibroblast proliferation associated with intercellular collagen was present around the surgical site. The thickness of the bleb was similar among all experimental groups, but it was significantly greater than in controls ( p < 0.05). The inflammatory area did not differ between the EX-PRESS and the silicone tube group but was significantly greater in the trabeculectomy group than in the tube group ( p = 0.031). A correlation between the thickness of the bleb wall and inflammation was found ( r = 0.56, p < 0.01). EX-PRESS and silicone tube implants appear to be relatively inert, with little difference in biocompatibility and bleb survival. Since some degree of inflammation was still observed histologically in the bleb, more noninvasive surgical methods and more biocompatible materials may be desirable.

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          Most cited references 25

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          Assessment of bleb morphologic features and postoperative outcomes after Ex-PRESS drainage device implantation versus trabeculectomy.

          To investigate bleb morphologic features and postoperative outcomes after Ex-PRESS drainage device (Alcon Laboratories) implantation versus trabeculectomy. Retrospective, consecutive case-control series. Information was collected from the charts of 35 consecutive Ex-PRESS procedures and 35 consecutive trabeculectomy procedures with at least 2 years of follow-up. Intraocular pressure (IOP), bleb morphologic features, reduction of dependence on medication, visual recovery, number of postoperative visits, and postoperative complication rates were compared between groups. Average follow-up was 28 months (standard deviation, 3.23 months). Mean IOP measurements were similar after 6 months, then became slightly higher in the Ex-PRESS group at 1 year and at the final follow-up (P = .004 and P = .008, respectively). Final percent IOP lowering was similar between groups (P = .209). Unqualified success was achieved in 77.14% of Ex-PRESS and 74.29% of trabeculectomy procedures at last follow-up (P = 1.00). An additional 5.71% and 8.57% reached qualified success for Ex-PRESS and trabeculectomy surgeries, respectively (P = .99). Evaluation by the Moorfields Bleb Grading System revealed less vascularity and height but more diffuse area associated with the Ex-PRESS blebs, although these differences were absent at study completion. There were fewer cases of early postoperative hypotony and hyphema and quicker visual recovery in the Ex-PRESS group. The Ex-PRESS group required fewer postoperative visits compared with the trabeculectomy group (P < .000). Success of Ex-PRESS surgery, as defined in our study, was similar to trabeculectomy. Final IOP measurements were slightly lower after trabeculectomy compared with Ex-PRESS. Differences in some postoperative outcomes faded with follow-up. There remains a need for long-term prospective studies comparing these 2 procedures. Copyright © 2011 Elsevier Inc. All rights reserved.
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            Comparison of polypropylene and silicone Ahmed Glaucoma Valves.

            To evaluate and compare the clinical outcomes after implantation of the silicone plate and the polypropylene plate Ahmed Glaucoma Valves. Prospective, multicenter, comparative series. A total of 132 patients with uncontrolled glaucoma were treated with either the silicone or polypropylene Ahmed Glaucoma Valve implant. Success was defined according to 2 criteria: (1) intraocular pressure (IOP) of 6 mmHg or more or 21 mmHg or less, and (2) IOP reduction of at least 30% relative to preoperative values. Eyes requiring further glaucoma surgery, including cyclophotocoagulation, or showing loss of light perception were classified as failures. Average follow-up was 12.8 months (range, 6-30 months) for the silicone plate group and 14.5 months (range, 6-30 months) for the polypropylene plate group (P = 0.063). At the last follow-up examination, the mean IOP was 13.8+/-3.9 mmHg and 17.3+/-6.5 mmHg (P<0.0001) and the mean number of antiglaucoma medications was 1.9+/-1.3 and 2.1+/-1.4 (P = 0.48) in the silicone plate and polypropylene plate groups, respectively. The life-table success rates for the silicone plate and polypropylene plate groups were 94.2% and 83.2% at 12 months and 82.4% and 56.7% at 24 months by definition 1, respectively (P = 0.035). When an IOP reduction of at least 30% was used for success criterion (definition 2), probabilities of success were 89.5% and 71.7% at 12 months and 78.3% and 68.5% at 24 months in the silicone and the polypropylene plate groups, respectively (P = 0.012). Visual outcomes were comparable between the 2 groups. However, complications including Tenon's cyst were observed more frequently in the polypropylene plate than in the silicone plate group (P<0.05). The silicone Ahmed Glaucoma Valve (model FP7) showed improved IOP reduction compared with the polypropylene (model S2) implant. Differences observed in mean IOP, success rate, and complications suggest that plate material may influence clinical outcome.
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              Comparison of different biomaterials for glaucoma drainage devices: part 2.

              Inflammation associated with biomaterials may contribute to the failure of glaucoma drainage devices. To compare the inflammatory reaction associated with the insertion of Krupin silicone, Molteno polypropylene, and Acrosof end plates in the subconjunctival space of rabbits. Similar-sized glaucoma end plates made of 3 different biomaterials were sutured to the sclera in the superotemporal quadrant of the rabbit eye. Thirty eyes of 15 albino New Zealand rabbits were randomly assigned to the 3 groups. Conjunctival vascular hyperemia was graded in a masked fashion among the 3 groups. At the end of 3 weeks, the enucleated eyes were examined histologically and by scanning electron microscopy. Molteno polypropylene was associated with more inflammation both in clinical observations and based on histological grading. Silicone and Acrosof were associated with less intense inflammation. One polypropylene end plate was extruded on day 21. Polypropylene appears to be more inflammatory than silicone. Flexible biomaterials appear to be less inflammatory than rigid ones. Bleb failure following glaucoma drainage device implantation could be related to the biomaterial-associated inflammation. Choosing a biomaterial with the least inflammatory potential might enhance the success rate of the glaucoma drainage device. Arch Ophthalmol. 2000;118:1081-1084

                Author and article information

                Ophthalmic Res
                Ophthalmic Research
                S. Karger AG
                February 2021
                04 June 2020
                : 64
                : 1
                : 68-76
                aDepartment of Ophthalmology, Toho University Ohashi Medical Center, Tokyo, Japan
                bMolecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, Gifu, Japan
                cDepartment of Ophthalmology, Gifu University Graduate School of Medicine, Gifu, Japan
                Author notes
                *Kyoko Ishida, Department of Ophthalmology, Toho University Ohashi Medical Center, 2-22-36, Ohashi, Meguro-ku, Tokyo 153-8515 (Japan), kyoko.ish@gmail.com
                509135 Ophthalmic Res 2021;64:68–76
                © 2020 The Author(s) Published by S. Karger AG, Basel

                This article is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND). Usage and distribution for commercial purposes as well as any distribution of modified material requires written permission. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 5, Tables: 2, Pages: 9
                Research Article

                Vision sciences, Ophthalmology & Optometry, Pathology

                Inflammation, Bleb, Glaucoma surgery, Glaucoma


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