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      • Record: found
      • Abstract: found
      • Article: found

      Effect of Pneumatic Suction Ring Placement on Intraocular Pressure in Cats

      research-article
      Ophthalmic Research
      S. Karger AG
      Cat, Intraocular pressure, Pneumatic suction ring

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          Abstract

          Purpose: To determine the effect of placing a pneumatic suction ring on intraocular pressure (IOP) in the cat and to design an improved method to generate a stable elevation of IOP. Methods: A pneumatic suction ring was applied to the eye in cats while the IOP was monitored. Three groups of animals (10 per group) were used. A vacuum pressure of 450 mbar was applied in one step to eyes of group 1 (anesthetized) and to group 2 (euthanized) cats. In group 3 (anesthetized) cats, an initial vacuum pressure of 250 mbar was applied, followed by a vacuum of slowly increasing pressure at a rate of 5 mbar/min for a total of 40 min to 450 mbar. Results: After the one-step application of a vacuum (450 mbar) to the eyes of anesthetized cats (group 1), IOP peaked within the first minute from a basal value of 25 ± 2 mm Hg (mean ± SD) to 90 ± 7 mm Hg. It then rapidly decreased to 69 ± 2 mm Hg 5 min later and continued to decrease to 39 ± 4 mm Hg 40 min later. This sharp peak and decline of IOP were also observed in eyes of euthanized cats (group 2). The basal IOP of these eyes was 8 ± 1 mm Hg. It rose to 18 ± 2 mm Hg immediately after the application of vacuum pressure (450 mbar) and returned to the basal level 5 min later. In contrast, the eyes of group 3 receiving an initial vacuum of 250 mbar followed by a 5 mbar/min vacuum increment exhibited a rapid increase in IOP and a very stable plateau (mean IOP = 62–68 mm Hg), lasting the whole study period (40 min). Conclusion: IOP after a one-step application of a vacuum via a pneumatic suction ring is self-adjusting and declines rapidly over time. This decline in IOP can be overcome by a supplementary increment in vacuum pressure.

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          Most cited references1

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          • Abstract: found
          • Article: not found

          Flow of aqueous humor in the canal of Schlemm.

          A mathematical model is presented for the flow of aqueous humor in Schlemm's canal in the eye. The model introduces a canal segment between two collector channels as a rectangular channel with porous upper wall. Two cases have been considered in the model: (I) the inner porous wall of the canal is rigid; (II) the inner wall is collapsible. Analytical solution of the governing equation in case I is straightforward, whereas the nonlinear equation in case II is solved by an iterative procedure. Aqueous fluid pressure and flow profiles in the proposed model are drawn, and the effects of important parameters on these profiles are brought out and discussed. It is concluded that for case I, resistance to aqueous flow is influenced by the filtration constant of the trabecular and endothelial meshwork and that narrowing of the canal reduces outflow. In case II, an increase in intraocular pressure (IOP) or compliance coefficient of the canal inner wall increases the collapse of the canal, which offers increased resistance to flow resulting in the decreased flow whereas increasing filtration constant facilitates aqueous outflow. These theoretical results suggest that increased IOP or decreased rigidity of the inner wall may contribute to the development of increased resistance as observed in some cases of glaucoma and that increasing values of filtration constant may contribute to the facility of outflow increase.
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            Author and article information

            Journal
            ORE
            Ophthalmic Res
            10.1159/issn.0030-3747
            Ophthalmic Research
            S. Karger AG
            0030-3747
            1423-0259
            2001
            October 2001
            01 October 2001
            : 33
            : 5
            : 271-275
            Affiliations
            Dean A. McGee Eye Institute, University of Oklahoma Health Science Center, Oklahoma City, Okla., USA
            Article
            55680 Ophthalmic Res 2001;33:271–275
            10.1159/000055680
            11586060
            36849863-aa57-44e8-8b31-5dd4b1768992
            © 2001 S. Karger AG, Basel

            Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. 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.

            History
            Page count
            Figures: 4, References: 15, Pages: 5
            Categories
            Original Paper

            Vision sciences,Ophthalmology & Optometry,Pathology
            Intraocular pressure,Cat,Pneumatic suction ring

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