Do the majority of post-ganglionic parasympathetic fibers from the ciliary ganglion primarily innervate the sphincter muscle or ciliary muscle?

The post-ganglionic parasympathetic fibers from the ciliary ganglion primarily innervate the ciliary muscle, which plays a crucial role in the process of accommodation. Accommodation refers to the eye's ability to change focus from distant to near objects, and this is accomplished when the ciliary muscle contracts. This contraction allows the lens to become more rounded, increasing its refractive power to focus on nearer objects.

In contrast, while the iris sphincter muscle, responsible for constricting the pupil, also receives some innervation from parasympathetic fibers, the majority of the fibers originating from the ciliary ganglion are directed towards the ciliary muscle. Thus, understanding the functional role of the ciliary muscle in accommodation highlights why the primary innervation from the ciliary ganglion is geared towards this muscle rather than the sphincter muscle of the iris.