Lens accommodation refers to dynamic changes in the shape and optical power of the lens to maintain focus on objects at varying distances [1]. The primary mechanism involves the ciliary muscle and zonular fibers altering lens curvature and thickness [2].

In the unaccommodated state for distant vision, parasympathetic input to the ciliary muscle is low. This allows the zonular fibers to pull taut on the lens capsule, flattening the lens [3]. Accommodation for near vision involves increased parasympathetic activation of the ciliary muscle, mediated by the Edinger-Westphal nucleus [4]. Contraction of the circular ciliary muscle reduces zonular fiber tension, allowing the elastic lens to increase convexity and optical power [5].

The cortical and subcortical pathways driving accommodation involve visual processing areas like the striate cortex and superior colliculi, which project to the Edinger-Westphal nucleus [6]. Preganglionic neurons then synapse on ciliary ganglion cells, whose postganglionic fibers directly innervate the ciliary muscle to dynamically adjust lens shape for focusing. Age-related declines in lens elasticity lead to reduced amplitude of accommodation and presbyopia.