Abstract
Purpose :
The viscoelastic properties of the crystalline lens play an important role in vision health. There is strong evidence that the development of presbyopia and cataract in the lens correlates with the age-related changes in lens biomechanical properties. In this work, we used dynamic optical coherence elastography (OCE) to measure the surface wave dispersion in the lens inside the eyeball ex-vivo and to evaluate age-related changes in both the elasticity and viscosity of the rabbit lens.
Methods :
Fifteen fresh rabbit eyes (Pel-Freez Biologicals, LLC, Rogers, AR) were separated into two groups: young (from two to three months old, N=5) and mature (over six months old, N=10). The OCE system colmbined a single-element ultrasound transducer (model ISO 304HP; CTS Valpey Corporation, Hopkinton, MA) with a spectral-domain optical coherence tomography system. The ultrasound transducer had a focal length of about 19 mm and a central frequency of 3.5 MHz. Five single-tone acoustic radiation force bursts ranging from 500 Hz to 2500 Hz were focused on the lens surface. A Kelvin-Voigt viscoelastic model and Scholte wave model were used to quantify the lens elastic and viscous shear moduli.
Results :
The average dispersion curves (i.e., phase velocity vs. frequency) for the young rabbit group and mature group and their respective fitting to the model are presented in Fig. 1. As seen in Fig. 1, the surface wave in mature lenses demonstrates higher speed in comparison with young lenses in the whole frequency range. Figure 2 shows the estimations of Young's modulus and the shear viscosity coefficient for two age groups calculated based on the theoretical model. The results demonstrated that the young lenses are softer and less viscous than the mature lenses.
Conclusions :
In this study, the dispersion of the surface waves in rabbit lenses was measured inside the eyeball. Based on these measurements, the elasticity and viscosity of the lenses were quantified for young and mature rabbits. The results demonstrate an increase in both stiffness and viscosity of the lenses with age. In our future work, we will use dynamic OCE to measure lens biomechanical properties as a function of age in vivo.
This work was supported by grant NIH R01EY030063 from the NationalInstitute of Health, Bethesda, MD, USA.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.