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      Multifocal Electroretinography Changes in the Macula at High Altitude: A Report of Three Cases

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          Abstract

          Background: To evaluate the short- and long-term effects of high-altitude hypobaric hypoxia on macula morphology and function during ascents, acclimatizations, and descents between 500 m and 5,650 m, macula function was evaluated in three healthy climbers of a trekking expedition. Methods:Macula physiology was tested with multifocal electroretinography (MF ERG), near and farvisual acuity, and Amsler grid tests. Macula morphology was tested with optical coherence tomography (OCT) and with stereoscopic fundoscopy obtained 1 week before ascent, as well as 1 week and 2 weeks after high-altitude exposure. The following physiological parameters indicative of acclimatization were compared daily during the expedition at altitudes between 500 m and 5,050 m: hemoglobin, oxygen saturation, resting heart rate, retinal findings, and the Lake Louise score of acclimatization. Results: The central macula MF ERG responses were significantly reduced 1 week after high-altitude exposure, and had recovered by the follow-up examination performed during the following week. Near visual acuity and Amsler grid tests remained unaffected at both follow-up examinations. No significant changes were found in the follow-up OCT and daily fundoscopy examinations in all three well-acclimatized climbers. Conclusions: High-altitude hypobaric hypoxia affects the function of the highly sensitive macula region. This suggests that the exposure of persons with macula diseases such as age-related macula degeneration, tapetoretinal degeneration, or diabetic retinopathy to high altitudes may influence the disease progression. For this reason, this population should avoid prolonged and unnecessary high-altitude exposure without proper acclimatization.

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          Most cited references16

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          Oxidative Stress During Myocardial Ischaemia and Heart Failure

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            High-altitude retinopathy.

            Thirty-nine healthy subjects were examined before and after a stay at 5,360 m by ophthalmoscopy and by retinal photography. Twenty of them were also tested for visual acuity, scotomata, and capillary leakage. Vascular engorgement and tortuosity and disc hyperemia were seen in all subjects at altitude and are a "normal" response to hypoxia. Twenty-two (56%) of the subjects had retinal hemorrhages and one showed "cotton-wool spots". These changes are abnormal reactions and are considered high-altitude retinopathy. After maximal exertion on a cycle ergometer, fresh hemorrhages were observed in seven of 34 subjects. The incidence of hemorrhage associated with exercise was significantly greater than predicted. Fluorescein leakage was noted after exercise in eight of 20 persons tested and was associated with exercise-induced hemorrhages. Two persons developed premacular hemorrhages.
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              Functional characterization of retina and optic nerve after acute ocular ischemia in rats.

              To functionally characterize the status of the rat retina and optic nerve after acute elevation of intraocular pressure (IOP) and to determine the dynamics of the pathologic changes in the ischemic retina and optic nerve. Retinal ischemia was induced in rats by acutely increasing the IOP (110 mm Hg/60 minutes). Direct and indirect pupil light reflexes (PLRs) were recorded from the noninjured eye, and electroretinograms (flash and flicker ERG) were recorded from the injured and control eyes before and after surgery. Amplitudes and latencies were calculated for each recording session. Preoperative PLR(ratio)s (indirect/direct PLR) were 76.7 +/- 2.6 (mean +/- SEM). Twenty-four hours after surgery the PLR(ratio) was 15.2 +/- 12.8, 10 days after surgery, 11.6 +/- 9.8; 20 days after surgery, 26.5 +/- 8.0; and 28 days after surgery, 33.27 +/- 9.3. However, at day 35, the PLR had significantly recovered (41.1 +/- 7.3) when compared with the 24-hour postoperative ratios (P < 0.01, repeated-measures ANOVA). Forty-two days after surgery, the PLR(ratio) started to decrease once again in the injured eyes (28.7 +/- 5.9). Electroretinographic amplitudes (full-field flash ERG) followed a similar pattern. Cone responses (flicker ERG) were measured 42 days after surgery and revealed defects in injured eyes (control eyes: 46.6 +/- 2.9 microV, injured eyes: 3.4 +/- 1.7 microV). Histologic analysis revealed ischemic damage to all retinal layers, with the primary defects localized to the central retina. Acute ocular ischemia causes a significant decrease in retinal function, as measured by PLR and ERG, although over time the rat retina and optic nerve show partial regain of function.
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                Author and article information

                Journal
                OPH
                Ophthalmologica
                10.1159/issn.0030-3755
                Ophthalmologica
                S. Karger AG
                0030-3755
                1423-0267
                2005
                November 2005
                16 November 2005
                : 219
                : 6
                : 404-412
                Affiliations
                aUniversity Eye Hospital Münster, Münster, Germany; bUniversity Eye Hospital Athens, Leoforos Mesogeion, Athens, Greece
                Article
                88387 Ophthalmologica 2005;219:404–412
                10.1159/000088387
                16286804
                76310f58-f1de-4ad1-8bd9-5cc6732eac55
                © 2005 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
                : 25 November 2004
                Page count
                Figures: 3, References: 36, Pages: 9
                Categories
                Case Report

                Vision sciences,Ophthalmology & Optometry,Pathology
                High altitude,Optical coherence tomography,Multifocal electroretinography,Macula dysfunction

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