The ciliary body is divided into two main regions:
1. Pars Plicata
- Location: Anterior portion of the ciliary body, closer to the iris.
- Structure: Contains ciliary processes, which are radial folds in the ciliary body.
- Function: The ciliary processes produce aqueous humor, which nourishes the lens and cornea and maintains intraocular pressure.
2. Pars Plana
- Location: Posterior portion of the ciliary body, closer to the ora serrata (the serrated junction between the retina and the ciliary body).
- Structure: This region is relatively flat and smooth compared to the pars plicata.
- Function: The pars plana does not produce aqueous humor. It is often used as a site for surgical access to the vitreous humor, such as in pars plana vitrectomy, because it is relatively avascular (fewer blood vessels) and less likely to cause damage to other structures.
These regions are anatomically and functionally distinct, with the pars plicata being crucial for aqueous humor production and the pars plana being useful for surgical access to the posterior segment of the eye.