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      • Record: found
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      Correcting magnification error in foveal avascular zone area measurements of optical coherence tomography angiography images with estimated axial length

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          Abstract

          Background

          To generate and validate a method to estimate axial length estimated (AL est) from spherical equivalent (SE) and corneal curvature [keratometry (K)], and to determine if this AL est can replace actual axial length (AL act) for correcting transverse magnification error in optical coherence tomography angiography (OCTA) images using the Littmann-Bennett formula.

          Methods

          Data from 1301 participants of the Raine Study Gen2-20 year follow-up were divided into two datasets to generate (n = 650) and validate (n = 651) a relationship between AL, SE, and K. The developed formula was then applied to a separate dataset of 46 participants with AL, SE, and K measurements and OCTA images to estimate and compare the performance of AL est against AL act in correcting transverse magnification error in OCTA images when measuring the foveal avascular zone area (FAZA).

          Results

          The formula for AL est yielded the equation: AL est = 2.102K − 0.4125SE + 7.268, R 2 = 0.794. There was good agreement between AL est and AL act for both study cohorts. The mean difference [standard deviation (SD)] between FAZA corrected with AL est and AL act was 0.002 (0.015) mm 2 with the 95% limits of agreement (LoA) of − 0.027 to 0.031 mm 2. In comparison, mean difference (SD) between FAZA uncorrected and corrected with AL act was − 0.005 (0.030) mm 2, with 95% LoA of − 0.064 to 0.054 mm 2.

          Conclusions

          AL act is more accurate than AL est and hence should be used preferentially in magnification error correction in the clinical setting. FAZA corrected with AL est is comparable to FAZA corrected with AL act, while FAZA measurements using images corrected with AL est have a greater accuracy than measurements on uncorrected images. Hence, in the absence of AL act, clinicians should use AL est to correct for magnification error as this provides for more accurate measurements of fundus parameters than uncorrected images.

          Supplementary Information

          The online version contains supplementary material available at 10.1186/s40662-022-00299-x.

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          Most cited references43

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          STATISTICAL METHODS FOR ASSESSING AGREEMENT BETWEEN TWO METHODS OF CLINICAL MEASUREMENT

          J. Martin Bland, DouglasG. Altman (1987)
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            Improvements on Littmann's method of determining the size of retinal features by fundus photography.

            A G Bennett, A R Rudnicka, D F Edgar (1994)
            Littmann's formula relating the size of a retinal feature to its measured image size on a telecentric fundus camera film is widely used. It requires only the corneal radius, ametropia, and Littmann's factor q obtained from nomograms or tables. These procedures are here computerized for practitioners' convenience. Basic optical principles are discussed, showing q to be a constant fraction of the theoretical ocular dimension k', the distance from the eye's second principal point to the retina. If the eye's axial length is known, three new methods of determining q become available: (a) simply reducing the axial length by a constant 1.82 mm; (b) constructing a personalized schematic eye, given additional data; (c) ray tracing through this eye to extend calculations to peripheral retinal areas. Results of all these evaluations for 12 subjects of known ocular dimensions are presented for comparison. Method (a), the simplest, is arguably the most reliable. It shows good agreement with Littmann's supplementary procedure when the eye's axial length is known.
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              How genetic is school myopia?

              Ian Morgan, K. Rose (2004)
              Myopia is of diverse aetiology. A small proportion of myopia is clearly familial, generally early in onset and of high level, with defined chromosomal localisations and in some cases, causal genetic mutations. However, in economically developed societies, most myopia appears during childhood, particularly during the school years. The chromosomal localisations characterised so far for high familial myopia do not seem to be relevant to school myopia. Family correlations in refractive error and axial length are consistent with a genetic contribution to variations in school myopia, but potentially confound shared genes and shared environments. High heritability values are obtained from twin studies, but rest on contestable assumptions, and require further critical analysis, particularly in view of the low heritability values obtained from parent-offspring correlations where there has been rapid environmental change between generations. Since heritability is a population-specific parameter, the values obtained on twins cannot be extrapolated to define the genetic contribution to variation in the general population. In addition, high heritability sets no limit to the potential for environmentally induced change. There is in fact strong evidence for rapid, environmentally induced change in the prevalence of myopia, associated with increased education and urbanisation. These environmental impacts have been found in all major branches of the human family, defined in modern molecular terms, with the exception of the Pacific Islanders, where the evidence is too limited to draw conclusions. The idea that populations of East Asian origin have an intrinsically higher prevalence of myopia is not supported by the very low prevalence reported for them in rural areas, and by the high prevalence of myopia reported for Indians in Singapore. A propensity to develop myopia in "myopigenic" environments thus appears to be a common human characteristic. Overall, while there may be a small genetic contribution to school myopia, detectable under conditions of low environmental variation, environmental change appears to be the major factor increasing the prevalence of myopia around the world. There is, moreover, little evidence to support the idea that individuals or populations differ in their susceptibility to environmental risk factors.
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                Author and article information

                Contributors
                Fred K. Chen: fredchen@lei.org.au
                Journal
                Journal ID (nlm-ta): Eye Vis (Lond)
                Journal ID (iso-abbrev): Eye Vis (Lond)
                Title: Eye and Vision
                Publisher: BioMed Central (London )
                ISSN (Electronic): 2326-0254
                Publication date (Electronic): 1 August 2022
                Publication date PMC-release: 1 August 2022
                Publication date Collection: 2022
                Volume: 9
                Electronic Location Identifier: 29
                Affiliations
                [1 ]GRID grid.1012.2, ISNI 0000 0004 1936 7910, Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute), , The University of Western Australia, ; Perth, WA Australia
                [2 ]GRID grid.415306.5, ISNI 0000 0000 9983 6924, Garvan Institute of Medical Research, ; Sydney, Australia
                [3 ]GRID grid.1008.9, ISNI 0000 0001 2179 088X, Ophthalmology, Department of Surgery, , University of Melbourne, ; East Melbourne, VIC Australia
                [4 ]GRID grid.410670.4, ISNI 0000 0004 0625 8539, Centre for Eye Research Australia, , Royal Victorian Eye and Ear Hospital, ; East Melbourne, VIC Australia
                [5 ]GRID grid.5475.3, ISNI 0000 0004 0407 4824, Surrey Biophotonics, Centre for Vision, Speech and Signal Processing and School of Biosciences and Medicine, , The University of Surrey, ; Guildford, UK
                [6 ]GRID grid.83440.3b, ISNI 0000000121901201, Institute of Ophthalmology, , University College London, ; London, UK
                [7 ]GRID grid.1489.4, ISNI 0000 0000 8737 8161, Lions Eye Institute, ; 2 Verdun Street, Nedlands, WA 6009 Australia
                Article
                Publisher ID: 299
                DOI: 10.1186/s40662-022-00299-x
                PMC ID: 9341098
                PubMed ID: 35909098
                SO-VID: a0faec3d-4056-4106-a046-5135fedcfdad
                Copyright © © The Author(s) 2022
                License:

                Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

                History
                Date received : 6 January 2022
                Date accepted : 6 July 2022
                Categories
                Subject: Research
                Custom metadata
                issue-copyright-statement © The Author(s) 2022

                Keywords: octa,keratometry,spherical equivalent,axial length,littmann-bennett formula
                Data availability:
                Keywords: octa, keratometry, spherical equivalent, axial length, littmann-bennett formula

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