Investigation of pulsatile retinal deformation as new biomechanical descriptor of the human ocular dynamics for glaucoma prognosis.

Hidalgo-Aguire, Maribel (2018). Investigation of pulsatile retinal deformation as new biomechanical descriptor of the human ocular dynamics for glaucoma prognosis. Thèse. Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 176 p.

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Résumé

Glaucoma is the second leading cause of blindness worldwide. The facts that glaucoma does not present any symptoms until major visual loss has occurred and that the primary causes of this neuropathy remain unknown make it challenging for both, diagnosis and treatment. While elevated intraocular pressure (IOP) remains the primary risk factor, other parameters such as low ocular perfusion pressure, ocular blood flow and the elasticity of the sclera and lamina cribrosa have been identified in the last years as additional factors potentially influencing the risk, prevalence and progression of the glaucomatous neuropathy. Theoretically, an individual’s susceptibility to IOP is in part determined by the eye geometry and tissue anatomy, therefore, it seems natural to consider biomechanics as framework for explaining how IOP-related stress and strain influence the physiology and pathophysiology of the connective, neural and vascular tissue, causing the changes on the structural and functional integrity of the optic nerve observed in glaucoma. The key challenge is then to understand how ocular biomechanics, in combination with the aforementioned risk factors, are transduced into tissue damage. It has been demonstrated that glaucoma is directly related with blood flow deficiencies in the retinal and choroidal circulation. The choroid has the highest blood flow per gram tissue of any organ in the human body and this flow is 80 % pulsatile. This pulsatility has been hypothesized to drive the retina forward while expanding the sclera, leading to a pulsatile deformation of the axons traveling from the retina and through the lamina cribrosa to the brain. If we consider that the mechanical properties of the tissues are also altered during the progression of the disease, then is very likely that such deformation may change. Within this framework, the present work is centered on the study and characterization of the peripapillary retinal tissue deformation due to choroidal vascular pulsatility and its possible implication in axonal damage and loss of the retinal nerve fiber layer in glaucoma. The general strategy designed to perform such investigation is to use video rate optical coherence tomography images of the optic nerve head combined with fully automated image analysis algorithms specially developed to measure and determine retinal deformation. A cross-sectional study was then carried out at the ophthalmology clinic of the Maisonneuve-Rosemont Hospital to evaluate peripapillary retinal deformation on patients that cover the most representative part of the glaucoma spectrum. The obtained results show that healthy eyes have significantly larger deformation of the peripapillary retina compared with the glaucoma spectrum. The measured deformation correlates differently with the principal risk factors of the glaucomatous neuropathy depending on diagnosis. Reduced retinal displacement proved to be related to glaucoma progression predictors showing that the biomechanical properties of the eye are altered even when there is no evident changes in the optic nerve head structure. Due to the versatility of the segmentation algorithm, it was possible to carry out a preliminary study to investigate retinal deformation around the macula using images previously acquired from a different clinic study. In this case, perifoveal retinal deformation in healthy eyes resulted to be significantly larger than in early glaucoma. Furthermore, ocular rigidity as well as changes in ocular volume were correlated with perifoveal retinal displacement in healthy eyes, which confirms that the observed deformation is driven by choroidal pulsatility. All these results suggest that the amount of retinal deformation should be further investigated since it could be potentially used as a new biomechanical descriptor of the eye for early diagnosis and assessment of glaucoma progression.

Type de document:	Thèse Thèse
Directeur de mémoire/thèse:	Costantino, Santiago
Co-directeurs de mémoire/thèse:	Lesk, Mark R.; Ozaki, Tsuneyuki
Mots-clés libres:	optic nerve head; glaucoma; image processing; optical coherence tomography; ocular biomechanics; ocular dynamics; retinal deformation
Centre:	Centre Énergie Matériaux Télécommunications
Date de dépôt:	19 oct. 2018 15:36
Dernière modification:	19 oct. 2018 15:36
URI:	http://espace.inrs.ca/id/eprint/7640

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