Journal of The Royal Society Interface
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In vivo optic nerve head biomechanics: performance testing of a three-dimensional tracking algorithm

Michaël J. A. Girard

Michaël J. A. Girard

Department of Bioengineering, National University of Singapore, Singapore, Republic of Singapore

Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore

Department of Bioengineering, Imperial College London, London, UK

[email protected]

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Nicholas G. Strouthidis

Nicholas G. Strouthidis

Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore

NIHR Biomedical Research Centre, Moorfields Eye Hospital and UCL Institute of Ophthalmology, London, UK

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Adrien Desjardins

Adrien Desjardins

Department of Medical Physics and Bioengineering, University College London, London, UK

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Jean Martial Mari

Jean Martial Mari

Department of Bioengineering, Imperial College London, London, UK

INSERM 1032, Université de Lyon, Lyon, France

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C. Ross Ethier

C. Ross Ethier

Department of Bioengineering, Imperial College London, London, UK

Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, GA, USA

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    Measurement of optic nerve head (ONH) deformations could be useful in the clinical management of glaucoma. Here, we propose a novel three-dimensional tissue-tracking algorithm designed to be used in vivo. We carry out preliminary verification of the algorithm by testing its accuracy and its robustness. An algorithm based on digital volume correlation was developed to extract ONH tissue displacements from two optical coherence tomography (OCT) volumes of the ONH (undeformed and deformed). The algorithm was tested by applying artificial deformations to a baseline OCT scan while manipulating speckle noise, illumination and contrast enhancement. Tissue deformations determined by our algorithm were compared with the known (imposed) values. Errors in displacement magnitude, orientation and strain decreased with signal averaging and were 0.15 µm, 0.15° and 0.0019, respectively (for optimized algorithm parameters). Previous computational work suggests that these errors are acceptable to provide in vivo characterization of ONH biomechanics. Our algorithm is robust to OCT speckle noise as well as to changes in illumination conditions, and increasing signal averaging can produce better results. This algorithm has potential be used to quantify ONH three-dimensional strains in vivo, of benefit in the diagnosis and identification of risk factors in glaucoma.

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