Background: To evaluate the age-related changes in the stiffness of the human lens nucleus in vivo.
Methods: A total of 78 volunteers with best-corrected visual acuity of 20/20with a mean ± standard deviation intraocular pressure (IOP) of 16 ± 2.5 mmHg were divided into 3 groups of 26. The mean ages of Groups A, B and C were 81 ± 5.5, 44 ± 3.2 and 21 ± 2.5 years, with mean axial lengths of 23.8 ± 0.5 mm, 23.8 ± 0.4 mm and 23.9 ± 0.3 mm, respectively. Using an elastographer, the ultrasound echolucency and elastic strain rate of the lens nucleus of one eye, selected randomly, of each subject were measured three times. The strain rate of the lens cortex could not be assessed. The qualitative differences in the strain rates across the groups were assessed, and differences in the strain rate ratios of the lens nuclei across groups were analysed by one-way ANOVA.
Results: The strain rates of the lens nuclei of Group A were much lower than those in Groups B and C, as assessed qualitatively; the elastograph images of the lens nuclei of the older group showed a blue colour.The strain rate ratios of the lens nuclei of Groups A, B and C were 0.02 ± 0.08, 0.69 ± 0.12 and 1.95 ± 0.85, respectively. The differences in the lens nucleus strain rate ratios across the groups were statistically significant, with p-values < 0.05.
Conclusions: Ultrasound elastography demonstrated in vivo that an older age is associated with a statistically significantly lower lens nucleus strain rate ratio and therefore a markedly higher lens nuclear stiffness.
Keywords: Age; Human lens nucleus; Stiffness; Strain rate ratio; Ultrasound elastography.