Contribution of the Ciliary Body to the Forces Measured During Simulation of Accommodation

Abstract

Purpose:: To measure the contribution of the ciliary body to forces measured during stretching of lenses maintained in the zonule-ciliary body-sclera framework.

Methods:: Post-mortem cynomolgus monkey (n=8; age: 3.75-9.4 years; <2 days postmortem) including the lens, capsule, zonules, ciliary body, and sclera were mounted in an optomechanical lens stretching system (EVAS I, Parel, ARVO 2002). Starting at zero load, the lenses were symmetrically stretched in step-wise fashion in 0.25mm steps. The load and inner ciliary body diameter were measured at each step and the diameter-load relationship was quantified. The lens was then removed from the system by carefully cutting completely through the zonules and hyaloid membrane and the intact ciliary body-sclera system was then stretched alone. The load and inner ciliary body diameter was measured at each step and the diameter-load relationship was quantified. The ciliary body diameter and load-diameter responses with and without the lens were compared.

Results:: The unstretched ciliary body diameter increased when the lens was removed from 9.0mm to 10.2mm. The total change in ciliary body diameter induced by stretching was higher once the lens was removed (0.48mm with lens; 0.91mm without lens). The load-diameter responses of the ciliary body with and without the lens were linear, with a slope of 14.43g/mm with the lens and 4.14g/mm without the lens.

Conclusions:: The ciliary body alone accounts for approximately 30% of the load recorded during ex vivo stretching experiments.Support: NIH EY14225; NSF Graduate Student Fellowship; NIH F31EY015395; Vision CRC, Sydney Australia; NIH center grant P30-EY014801; Research to Prevent Blindness; Henri and Flore Lesieur Foundation.

Keywords: ciliary body • ciliary muscle • presbyopia