Age-Dependent Changes in Non-Human Primate Lens Surface Curvatures During Simulated Accommodation

Abstract

Purpose: : To measure changes in lens curvatures during ex vivo simulated accommodation of cynomolgus monkey and hamadryas baboon lenses as a function of age.

Methods: : Lens shape and power were measured during ex vivo simulated accommodation on 11 cynomolgus (1.4-9.8 y/o) monkey lenses from 11 donors (PMT 19.1 ± 14.3 hours) and 9 hamadryas baboon (4-21 y/o) lenses from 8 donors (PMT = 7.1 ± 9.4 hrs). Tissue sections (lens, capsule, zonules, ciliary body, and sclera) were mounted in a 2^nd-generation lens stretching system (EVAS II) and radially stretched in a stepwise fashion from the accommodated (zero-load) to the unaccommodated state. The lens cross-sectional profile was imaged at every step increment with a custom designed OCT system. The images were processed to determine the anterior and posterior radii of curvature and asphericities at every step increment. A linear regression was performed on the changes in radii of curvatures as a function of the power change during stretching to obtain radii of curvature versus power slopes for each lens. A linear regression was then performed on the radii of curvature - power slope as a function of age to determine the age-dependency.

Results: : In all eyes, lens stretching flattened both surfaces and decreased the refractive power. For the cynomolgus monkeys, there was no significant age-dependent trend in the radii of curvature / power slope (anterior = 0.22 ± 0.1 mm/D, posterior = 0.07 ±0.01 mm/D). For the baboons, the anterior radii of curvature / power slope decreases with age (in mm/D: -0.14 - 0.007*Age) and the posterior radii of curvature / power slope was independent of age (in mm/D: 0.06 ±0.002).

Keywords: accomodation • optical properties • presbyopia