Surgery of Presbyopia with Accommodative Lenses

The ciliary body is a circular structure ( as appears in coronal section and triangular in cross section) forming a complete ring which is continuos anteriorly with the iris periphery and posteriorly with the choroid. It measures about 6mm wide (6.5-mm on temporal side and 5.5-mm on the nasal side) and extends forward to the scleral spur and backward to the ora serrata of the retina. It presents two main zones, the smooth pars plana (orbicularis ciliaris) posteriorly and the pars plicata (corona ciliaris) anteriorly. The equator of the lens is situated about 0.5-mm from the ciliary processes. The postganglionic parasympathetic fibers derived from the oculomotor nerve innervate the ciliary muscle via short ciliary nerves. As regards crystalline lens, it is a transparent, biconvex structure situated behind the iris and the pupil and in front of the vitreous body. The convexity of its anterior surface is less than that of its posterior surface. In the adult the lens measures approximately 10-mm in diameter and 4 mm thick. The equator of the lens is encircled by the ciliary processes of the ciliary body. Its capsule is an elastic membrane that envelops the entire lens. This elastic capsule can be stretched up to about 60% of its circumference without tearing. The capsule receives the insertion of the zonular fibers anteriorly and posteriorly at the lens periphery as well as at the lens equator. Suspensory ligament of the lens (ciliary zonule) consists of a series of fibers passing from the ciliary body to the lens forming a ring, holding the lens in position and enabling the ciliary muscle to act on it during accommodation. The zonules pass through the valleys between the ciliary processes to whose lateral walls they are closely attached by tension fibers. Tension fibers are thought to play an important role in the accommodation process by stabilizing the zonules. The zonular apparatus is always bent at the zonular fork, showing the strength of the anchorage of the zonular plexuses to the ciliary processes. This secondary anchorage is thought to be extremely important in relation to accommodation as it explains how an equatorial force is exerted upon the lens by fibers that originate partially in the pars plana.