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      Fixation Stability and Macular Light Sensitivity in Patients with Diabetic Maculopathy: A Microperimetric Study with a Scanning Laser Ophthalmoscope

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          Abstract

          Background: In patients with diabetic maculopathy, evaluation of visual acuity alone may not represent central retinal function sufficiently. Despite good visual acuity, patients may suffer from visual disturbances like waviness, relative scotoma, loss of fixation and decrease of contrast sensitivity. The aim of the study was to assess localized light sensitivity in the central visual field and to determine fixation stability in patients with diabetic maculopathy with moderate visual loss in comparison to healthy controls. Methods: Twenty-seven patients (mean age: 54 ± 15; range 17–81 years) with diabetic maculopathy and 61 controls (mean age: 45 ± 22; range 18–85 years) were included in the study. Light sensitivity was quantified by presenting stimuli with different light intensity with simultaneous real-time monitoring of the retina (intensity: 0–27.9 dB; size: Goldmann III, wavelength: 633 nm). Eye movements were controlled by semiautomatic fundus tracking. Fixation stability was quantified by measuring the area within 75% of all points of fixation. Results: Fixation stability was significantly decreased in diabetic patients in comparison to controls (43 ± 22 vs. 31 ± 16 arc min, p < 0.01). There was a significant difference in macular light sensitivity in diabetic patients compared to controls (19.6 ± 0.5 dB), both in mean difference (15.6 ± 1.4 dB) and if affected with macular edema (16.1 ± 4.5 dB), hard exudates (13.3 ± 6.7 dB), nonperfusion areas (10.3 ± 7.9 dB) and laser burns (3.0 ± 6.1 dB). Temporal parts of the macula were more affected than other parts. No correlation was found between visual acuity and foveal light sensitivity and foveal fixation, respectively. Conclusion: Macular light sensitivity decreased progressively with the kind and severity of retinal alteration independent of visual acuity. The assessment of macular light sensitivity and stability of fixation with automatic threshold microperimetry may help to identify patients with diabetic maculopathy and could improve the management of diabetic maculopathy.

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          Most cited references 12

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          Microperimetry of localized retinal nerve fiber layer defects.

          The aim of this study was to determine the sensitivity of retinal areas involved in a localized retinal nerve fiber layer (RNFL) defect and to assess correlations between microperimetry and the standard full threshold central 30 deg visual field test. Twenty-five patients with focal RNFL defects, evaluated by means of Argon-blue scanning laser ophthalmoscopy (SLO), underwent an automated 30 deg central visual field examination and a microperimetry with SLO. Microperimetry was performed according to standard procedures (infrared laser for fundus imaging; HeNe laser for 10 candles/m2 background illumination, fixation aid and generation of stimuli; manual fundus tracking). The size of stimuli was Goldmann III with 0.1 sec duration. In eyes with focal RNFL defects a deep microperimetric scotoma of at least 5 dB was found in 12 cases and a mild scotoma (1-4 dB) in 13 cases. These scotomas were mainly located throughout the whole defect or grouped in the temporal or nasal sides of the defect and were characterized by sharp and well-defined borders. With automated perimetry, a scotoma, defined by a single point depression of at least 10 dB or a depression of at least 5 dB in two or more contiguous points corresponding to the RNFL, defect, was found in only 14 out of 25 eyes with microperimetric defect. Focal RNFL defects correspond to localized areas of depressed retinal sensitivity as evaluated by microperimetry. The close correspondence between structural and microperimetric findings suggests that, in hypertensive eyes also, localized RNFL defects correspond to visual dysfunction possibly associated with substantial atrophy of ganglion cells.
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            Normal values for fundus perimetry with the scanning laser ophthalmoscope.

            To evaluate the normal light sensitivity values for fundus perimetry and their short time fluctuation (reliability) in normal volunteers of different ages. After the development of full-threshold static fundus perimetry, age-corrected sensitivity values for normal subjects are required to interpret results and to compare them with conventional computerized perimetry. Full-threshold fundus perimetry of the central field (33 x 21 degrees) by means of the scanning laser ophthalmoscope was performed on 152 eyes of 99 healthy persons aged 16 to 77 years with normal vision and no eye disease. Fixation was simultaneously documented. Light sensitivity values were evaluated according to each subject's age and test point location. Linear regression analysis disclosed a significant (P < .0001) decrease of the mean sensitivity of 0.275 dB per decade of increasing age, starting with 16.6 dB at age 10 years. Standard deviation around the center of fixation was 0.287 degrees in the first decade, and it increased by 2.82 minutes of arc per decade (P < .0001). Variation in triple examinations of subjects did not differ from short time fluctuation. Visual fields examined with fundus perimetry show reliable measurements in a range comparable to conventional computerized perimetry. There is a significant correlation between increase of age and decrease of light sensitivity in fundus perimetry. Visual fields obtained with fundus perimetry seem to correlate well with known data from computerized static threshold perimetry. It should be recognized that even in normal subjects, the stability of fixation decreases with increasing age.
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              Scanning laser ophthalmoscope microperimetry.

               C Scassa,  M Varano (1998)
              In this article, the methodologies and clinical applications of microperimetry performed by scanning laser ophthalmoscope (SLO) are described. This technique provides functional results by direct visualization of the macular area. We present the most interesting data about clinical applications in ocular pathology. SLO microperimetry is a new diagnostic tool in ophthalmic practice. It permits an exact, point-to-point correspondence between fundus image and perimetric results, impossible to achieve by projection perimetry, so representing the most suitable device for simultaneous fundus imaging and psychophysical testing. Microperimetry is performed by SLO (Rodenstock),1 which permits other applications. SLO microperimetry allows the real-time functional study of retinal sensitivity by direct ophthalmoscopic control of the retinal surface. Foveal or excentric fixation can be assessed as well. Instability of fixation during computerized perimetry is a possible misleading factor resulting in unexplainable findings, especially in eyes with decreased visual acuity. The main characteristic of microperimetry is the ability to see the stimuli presented on the retina in real time: this permits an accurate monitoring of fixation and correlation of anatomical or pathological features directly with retinal 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
                February 2005
                06 January 2005
                : 219
                : 1
                : 16-20
                Affiliations
                aAugenklinik, Universitätsklinikum der RWTH Aachen, Aachen, bAugenklinik, Albert-Ludwigs-Universität, Freiburg, cAugenklinik, Albert-Magnus-Universität, Leipzig und dAbteilung für Netzhaut- und Glaskörper-Chirurgie, Zentrum für Augenheilkunde der Universität zu Köln, Köln, Deutschland
                Article
                81777 Ophthalmologica 2005;219:16–20
                10.1159/000081777
                15627822
                © 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.

                Page count
                Figures: 2, Tables: 1, References: 33, Pages: 5
                Categories
                Original Paper

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