Biomechanics of the Aging Crystalline Lens

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With aging, every person experiences presbyopia, an eye condition leading to the inability to see far and near objects in sharp focus. Current treatment options for presbyopia, either surgical or with spectacles, only improve vision at a fixed distance but do not restore the ability to actively change the focus distance, which is called ?accommodation.? Visual accommodation is governed by the deformability of the crystalline lens of the eye, which determines the ability to vary lens shape and thus focusing distance. Therefore, the fundamental understanding of the biomechanics of the crystalline lens and its aging process could lead to novel treatments for presbyopia. However, measuring the mechanical properties of the intact lens is difficult because mechanical testing methods are generally based on physical contact. The research addresses this need with a novel imaging modality, Brillouin microscopy, which can map lens properties without contact at high 3D resolution. The overall goal of this research program is to measure the biomechanics aging crystalline lens tissue using Brillouin technology in order to develop biomechanically-efficient approaches to delay presbyopia onset, slow progression and perhaps to restore accommodation. This project will advance the fundamental understanding of the accommodation process, thus addressing long-standing open questions in the field and providing potential solutions to presbyopia. Novel Brillouin microscopy will provide three-dimensional maps of the elastic modulus inside the lens and of its age-related changes. Development of a computational model of lens biomechanics and validation against gold-standard mechanical tests will enable testing the hypothesis that the spatial distribution of elastic modulus within the lens should be targeted to delay presbyopia onset or restore dynamic accommodation. Brillouin measurements and the validated model will be used to design and test three potential avenues to presbyopia-correction, i.e. limiting lens growth, disrupting protein crosslinking, and light-based localized micro-cutting. These are potentially effective solutions in increasing lens deformability and are compatible with current technological capabilities. In broader terms, the comprehensive information provided by Brillouin imaging could yield mechanistic insights into how accommodation is related to the underlying molecular processes, such as protein expression and micro-structural changes, which are responsible for the mechanical properties of the lens.