Abstract
Purpose :
Presbyopia has no meditation to restore the accommodative ability of eye. Lens elasticity is decreased during aging. To investigate the biological cause of presbyopia, lens elasticity measurements in ex vivo model were designed.
Methods :
Under anesthesia with medetomidine, midazolam and butorphanol by intraperitoneal injection, lenses were collected from C75BL/6J male mice at 8 weeks and 52 weeks and Jcl:SD male rats at 8 weeks and 73-78 weeks. Lens elasticity was measured by using a device named YAWASA measuring Young’s modulus which was calculated from the stress required for 15% strain of lens diameter by extended Hertzian contact theory.
Results :
The 15% strain stress revealed significant elasticity difference between lenses from young and aged mice and rats. 15% strain stress was 0.00625±7.61x10e-4 (N) in young mice and 0.0349±6.36x10e-3 (N) (p=0.0030) in aged mice. In consistent with the result in mice, 15% strain stress was increased in rat during aging (Young rats’ was 0.0173 ±2.03x10e-3 (N), while aged rats’ was 0.0891±1.87x10e-2 (N) (p=0.0005).
Conclusions :
To the best of our knowledge, this is the first report that rat lens stiffness increases by age as well as mouse and human. The number of lenses tested was relatively small, there are statistically significant differences between elasticity of young and aged lenses in mouse and rat. Lens elasticity shift by age could be preserved in many mammalian species as previously reported in porcine and human. Our data show that lens elasticity is increased during aging both in mice and rats suggesting that YAWASA is a novel method to measure lens elasticity. The stiffness shift of lens during aging is considered to be involved with some reasons, for example intermolecular or intramolecular disulfide bond, non-disulfide bond, selective cleavage of α crystallin at the C-terminal, however the reason still remains unknown. From both of experimental and clinical view points, the method that lens elasticity could be detected without extractions of the lenses will be needed.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.