Age-Dependence of the Power-Load and Diameter-Load Responses of Human and Monkey Lenses During Simulation of Accommodation in a Lens Stretcher

Abstract

Purpose:: To quantify the age-related changes in the force required to change the human and monkey lens diameter and lens power.

Methods:: Experiments were performed on cynomolgus monkey (n=48; age: 3.8 to 11 years), rhesus monkey (n=35; age: 0.7 to 17 years), and human (n=20, age 8 to 70 years) eyes. Each eye was dissected to isolate the lens maintained in its supporting framework (zonules, ciliary body, and surrounding sclera). The lens was mounted in an optomechanical system that simulates accommodation by radially stretching the lens in a stepwise fashion. The stretching load, optical power and lens equatorial diameter were measured at each step. The diameter-load and power-load responses were fit with a linear model. The diameter-load (mm/g) and power-load (D/g) slopes were quantified as a function of age.

Results:: The average change in cynomolgus, rhesus, and human lens diameter was 0.094 mm/g, 0.109 mm/g and 0.069 mm/g in young lenses, and 0.069 mm/g, 0.067 mm/g and 0.036 mm/g in older lenses. For the same lenses, the average change in lens power was -3.73 D/g, -2.83 D/g and -1.22 D/g in young lenses and -2.46 D/g, -2.16 D/g and -0.49 D/g in older lenses. No changes in diameter or power could be produced in presbyopic human lenses.

Conclusions:: The force required to change the lens diameter and lens power increases with age in human and monkey lenses. Our results agree with presbyopia theories that predict that the force required to disaccommodate the lens increases with age.Support: NIH Grant EY14225; NIH F31 EY015395 (Borja); Florida Lions Eye Bank; Vision CRC, Sydney, Australia; NSF Graduate Student Fellowship (Ziebarth); NIH center grant P30-EY014801; Research to Prevent Blindness.; Henri and Flore Lesieur Foundation.

Keywords: presbyopia • optical properties • aging