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      Normal Values of Short-Wavelength Automated Perimetry

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          Abstract

          Background: The purpose of this study was to evaluate short-wavelength automated perimetry (SWAP, i.e., blue-yellow) in normal volunteers and to review the current normal values provided by the manufacturer. Methods: 28 eyes of 28 normal subjects (age range 21–48 years, mean age 36.5 years) had SWAP (Octopus 101, two phases of program G2, Interzeag AG, Schlieren, Switzerland). All subjects had normal eye examinations, refractive errors with spherical equivalents <5 diopters and astigmatism <2 diopters, normal intraocular pressures, no history of diseases affecting the visual field or nerve fiber layer, and normal white-white automated perimetry (Octopus 101, program G2). Results: 21% of the subjects (6/28) had to be excluded since visual field testing was not reliable (reliability factor >5%). With the normal values provided by the manufacturer, only 45% of the remaining subjects (10/22) had all other indices within normal limits. With the appropriate normal values based on the multicenter SWAP Octopus 101 study, 11% (3/28) were beyond the normal range: all had abnormal high sensitivities – 2 due to false-positive response. The normal value range for the index Mean Defect is remarkably wide (5.-, median, 95.- percentile: –4.4, –0.5, +5.3 dB, respectively). The normal value range for the index Loss Variance is surprisingly low and similar to standard perimetry (5.-, median, 95.- percentile: –1.7, 6.8, +21.2 dB<sup>2</sup>, respectively). Conclusion: SWAP with the Octopus G2 program reaches appropriate specificity but only if the correct normal values of the multicenter SWAP Octopus 101 study are used. The variability between subjects is remarkably large. The variability within a visual field is similar for SWAP and standard perimetry as reflected by similar values for the visual field index Loss Variance. Further studies have to establish the sensitivity to detect a disease for SWAP on the Octopus 101.

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          Most cited references 4

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          Short wavelength automated perimetry.

           Conor Wild (2001)
          Short Wavelength Automated Perimetry (SWAP) utilizes a blue stimulus to preferentially stimulate the blue cones and a high luminance yellow background to adapt the green and red cones and to saturate, simultaneously, the activity of the rods. This review describes the theoretical aspects of SWAP, highlights current limitations associated with the technique and discusses potential clinical applications. Compared to white-on-white (W-W) perimetry, SWAP is limited clinically by: greater variability associated with the estimation of threshold, ocular media absorption, increased examination duration and an additional learning effect. Comparative studies of SWAP and W-W perimetry have generally been undertaken on small cohorts of patients. The conclusions are frequently unconvincing due to limitations for SWAP in the delineation of abnormality and of progressive field loss. SWAP is almost certainly able to identify glaucomatous visual field loss in advance of that by W-W perimetry although the incidence of progressive field loss is similar between the two techniques. Increasing evidence suggests that functional abnormality with SWAP is preceded by structural abnormality of the optic nerve head and/or the retinal nerve fibre layer. SWAP appears to be beneficial in the detection of diabetic macular oedema and possibly in some neuro-ophthalmic disorders.
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            Test-retest variability of blue-on-yellow perimetry is greater than white-on-white perimetry in normal subjects.

            To compare long-term fluctuation of blue-on-yellow automated perimetry with white-on-white automated perimetry in normal subjects. White-on-white and blue-on-yellow automated perimetry were performed on a Humphrey Visual Field Analyzer and an Octopus perimeter, both modified for blue-on-yellow perimetry. The study sample consisted of 31 eyes of 31 normal subjects for the Humphrey perimeter and 33 eyes of 33 normal subjects for the Octopus perimeter. After one practice session, each subject completed four testing sessions over a period of 2 to 8 weeks, each separated by at least 1 day. Each testing session consisted of both white-on-white and blue-on-yellow perimetry performed on one eye; the order of the tests was alternated for successive sessions. Long-term fluctuation (expressed as statistical variance) was calculated for each test location. Intersubject variability (expressed as statistical variance) across all subjects was determined for each test location. On the Humphrey perimeter, the long term fluctuation for blue-on-yellow perimetry (4.07 +/- 3.07 dB2) was significantly greater than that for white-on-white perimetry (1.97 +/- 0.99 dB2; P < .001). Long-term fluctuation increased as a function of eccentricity for both blue-on-yellow and white-on-white perimetry. Short-term fluctuation was significantly greater for blue-on-yellow (0.46 +/- 0.25 dB) than that for white-on-white perimetry (0.29 +/- 0.19 dB; P < .02). Finally, the intersubject variability was significantly greater in blue-on-yellow (13.2 +/- 2.8 dB2) than it was in white-on-white perimetry (4.25 +/- 1.13 dB2; P < .001). Similar results were found with the Octopus perimeter. Long-term fluctuation and short-term fluctuation of blue-on-yellow perimetry are greater than those of white-on-white perimetry in normal subjects. The increased long-term fluctuation requires appropriate statistical approaches when evaluating serial change of blue-on-yellow perimetry.
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              Blue-on-yellow visual field and retinal nerve fiber layer in ocular hypertension and glaucoma.

              It has been suggested that the clinically detectable changes of the blue-on-yellow (B/Y) visual field and retinal nerve fiber layer (RNFL) may precede standard white-on-white (W/W) visual field defects in the progression of glaucoma. The aim of this study was to test the relationship between the results of B/Y visual fields and semiquantitative RNFL evaluation in corresponding areas and to determine how the B/Y visual fields and RNFL scores label the normal W/W perimetry hemifields in patients with glaucoma and ocular hypertension.
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                Author and article information

                Journal
                OPH
                Ophthalmologica
                10.1159/issn.0030-3755
                Ophthalmologica
                S. Karger AG
                0030-3755
                1423-0267
                2003
                August 2003
                17 June 2003
                : 217
                : 4
                : 260-264
                Affiliations
                aDepartment of Strabismus and Neuro-Ophthalmology, Kantonsspital St. Gallen, St. Gallen, and bUniversity Eye Clinic Basel, Basel, Switzerland
                Article
                70632 Ophthalmologica 2003;217:260–264
                10.1159/000070632
                12792131
                © 2003 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.

                Page count
                Tables: 4, References: 17, Pages: 5
                Categories
                Original Paper

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