Abstract
Presbyopia is a loss of the dynamic accommodation response of our vision and affects everybody as they age.
Presbyopia is not a static defect such as myopia since the lens must be capable of changing size and shape to
achieve different focal lengths. However, current treatment options today are based on spectacles, or static
corrections of vision, and do not treat the underlying cause to restore dynamic accommodation, resulting in
subpar corrections and problems with quality of life. Growing evidence suggests that stiffening of the lens is
critical to the inability of the eye to accommodate, and recent therapies have been developed targeting both the
optical and biomechanical nature of presbyopia, with varying levels of success. However, the major barrier to
innovation in this space is the lack of in vivo characterization and monitoring of lens accommodation mechanics,
which would aid both diagnostic monitoring and therapeutic planning. The lens presents spatially varying
mechanical properties that change with age, and thus monitoring this variation in vivo is important. Optical
coherence elastography (OCE) and Brillouin microscopy are two promising techniques in early clinical stages
but suffer from complementary limitations. While OCE can quantitatively measure elastic modulus in
physiological conditions, the contrast is limited in transparent tissues like the lens. Brillouin microscopy is capable
of high spatial resolution but so far has only provided relative stiffness measurements because the high-
frequency longitudinal modulus needs calibration, which is currently lacking in clinical settings. To address this
unmet need, we propose a combination OCE/Brillouin system capable of measuring co-located Brillouin spectra
and OCE information to map the depth-dependent elastic moduli. Combining OCE/Brillouin will allow for
quantitative evaluation of depth-dependent biomechanical properties of the lens in 3D and for the use of forward-
models to predict accommodation power and guide novel therapies. In Aim 1, the combined elastography system
specifications will be quantified to meet criteria for evaluating a human lens. In Aim 2, the effective elastic
modulus will be validated in an ex-vivo porcine lens for generating a biophysical model of accommodation.
Finally, the system will be field-tested in Aim 3 using in vivo lens measurements combined with a forward finite-
element model and validated against experimentally measured accommodation power. This research will
ultimately result in enabling patient-specific predictive models of accommodation changes from lens softening
procedures for presbyopia treatment.