Surface and Internal Power Change of the Non-Human Primate Crystalline Lens During Simulated Accommodation

Abstract

Purpose: : To determine the relation between curvature, total power, surface power, and internal power in hamadryas baboon and cynomolgus monkey lenses during accommodation.

Methods: : Shape and total power of 8 baboon lenses (5.4-8.3 years, PMT=22+/-14 hours) and 8 cyno lenses (6-8.4 years, PMT=14+/-17 hours) were measured during simulated accommodation in a lens stretcher. The lenses were stretched in discrete steps. At each step, power was measured with a Scheiner system and lens cross-section was imaged with a custom OCT system. The lens curvatures and axial thickness were calculated from the OCT images. Surface power was calculated using refractive indices of 1.336 for aqueous and 1.371 for outer cortex. Internal power was calculated by subtracting surface power from total power.

Results: : There was a linear trend between total power change and curvature change, with slopes of 0.10 D/D for the anterior baboon lens surface and 0.15 D/D for the posterior baboon and for the anterior and posterior monkey lens surfaces. These values correspond to a surface power change and internal power change per curvature change of 0.03D/D and 0.07 D/D for the anterior baboon and 0.04 D/D and 0.11 D/D for the posterior baboon and anterior and posterior monkey. The power-thickness trend was linear with a slope of 22.5 D/mm for baboons and 27.4 D/mm for monkeys.

Conclusions: : The internal structure of the lens contributes to the change in power during simulation of accommodation in non human primate lenses. The internal power change is more than twice the surface power change.Support: 2R01EY14225, 5F31EY15395 (DB); an unrestricted grant from Research to Prevent Blindness; Adventus Technology Inc; the Australian Government CRC Scheme through the Vision CRC; Florida Lions Eye Bank; P30EY14801 (Center Grant); Henri and Flore Lesieur Foundation(JMP).

Keywords: accommodation • presbyopia