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Sebastien Besner, Giuliano Scarcelli, Roberto Pineda, Seok Yun; Age-related Stiffening of Human Lens Measured by In Vivo Brillouin Microscopy. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4270.
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© ARVO (1962-2015); The Authors (2016-present)
The loss of accommodation power with age is thought to be related to the increase of the stiffness of the crystalline lens. More recently, evidences have shown that the change in the stiffness gradient may also play a dominant role in accommodation amplitude. In order to investigate the contribution of lens sclerosis to loss of accommodation with age, we present a novel optical, non-contact and non-destructive method based on Brillouin scattering, which measures the local elastic modulus of the crystalline lens in vivo with micron size resolution.
Brillouin confocal microscopy was performed on 5 dilated eyes (2.5% phenylephrine and 0.5% tropicamide) of 5 patients with an age range of 23 to 47 years. The Brillouin spectral shift, which is proportional to the longitudinal modulus of elasticity, was acquired along the optical axis of the crystalline lens with an axial resolution of about 60 microns and a lateral resolution of less than 10 microns. Ongoing study will include 10 eyes from 10 patients with age ranging between 20 and 60 years.
At all ages, the elastic modulus was found to increase from the lens cortex to the nucleus with a general steeper increase in the posterior part of the lens. The overall lens stiffness was found to increase with age (p<0.05). This is mainly due to the growth of the stiffer nucleus portion of the lens (R=0.91) and by the increase of the stiffness gradient from the cortex to the nucleus (R=0.65). Maximum elastic modulus (in the nucleus) and minimal elastic modulus (in the cortex) revealed no statistically significant age dependency.
Elastic modulus of the human crystalline lens was measured for the first time in vivo by using confocal Brillouin microscopy. For the age range of 23 to 47 years old, we found that the lens nucleus was stiffer than the lens cortex. We also observed a statistically significant increase of the stiffness of the lens with age. However, the observed age-related stiffening was not due to an increase of peak modulus with age, but rather to a variation of the spatial distribution of the elastic modulus inside the aging lens, where both nucleus thickness and stiffness gradient might play a role.
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